Ohm's Law Practice Questions — Armed Services Vocational Aptitude Battery (ASVAB)

Question 1Question →

Complete the statement regarding the electrical parameters of the DC circuit by calculating the missing resistance and current values.

Fill in the blanks below

An indicator lamp with a constant resistance draws

150\text{ mA}

when connected to a

24\text{ V}

direct current source. The internal resistance of the lamp is

\Omega

, and if the supply voltage is increased to

36\text{ V}

, the current drawn by the lamp will increase to

\text{mA}

.

Show answer & explanation

Answer

The internal resistance of the lamp is 160 Ω, and the new current at 36 V is 225 mA.

Converting

150\text{ mA}

to standard amperes yields

0.15\text{ A}

. Using Ohm's law (

R = V / I

), the internal resistance is

24\text{ V} / 0.15\text{ A} = 160\ \Omega

. When the voltage rises to

36\text{ V}

, applying

I = V / R

produces

36\text{ V} / 160\ \Omega = 0.225\text{ A}

, which corresponds to

225\text{ mA}

.

Step-by-Step Solution

1

Convert the nominal current from milliamperes to base amperes

I_1 = 150\text{ mA} = 0.15\text{ A}

Ohm's law requires base SI units (amperes, volts, ohms) for direct calculation.

2

Calculate the constant internal resistance using Ohm's law

R = \frac{V_1}{I_1} = \frac{24\text{ V}}{0.15\text{ A}} = 160\ \Omega

Resistance equals voltage divided by current.

3

Calculate the new current at the elevated voltage level

I_2 = \frac{V_2}{R} = \frac{36\text{ V}}{160\ \Omega} = 0.225\text{ A} = 225\text{ mA}

Current across a fixed resistance is directly proportional to applied voltage (

I = V / R

).

Key Concept

Ohm's Law (

V = I \times R

) and Direct Proportionality in DC Circuits

Estimated Time:45s

Question 2Question →

An auxiliary electric bilge pump operates on a $12\text{ V}$ DC power supply. If the internal electrical resistance of the pump motor is $6\ \Omega$ , what is the steady-state current drawn by the pump during operation?

0.5\text{ A}

2\text{ A}

6\text{ A}

72\text{ A}

Show answer & explanation

Answer: $2\text{ A}$

Answer

The current drawn by the pump is

2\text{ A}

.

According to Ohm's Law, current (

I

) equals voltage (

V

) divided by resistance (

R

). Dividing the

12\text{ V}

supply by the

6\ \Omega

load resistance yields exactly

2\text{ A}

.

Step-by-Step Solution

1

Identify the given circuit parameters and the formula to solve for unknown current.

Given: Voltage

V = 12\text{ V}

, Resistance

R = 6\ \Omega

. Ohm's Law states

V = I \times R

, which rearranges to

I = \frac{V}{R}

.

Ohm's Law defines the fundamental mathematical relationship between voltage, current, and resistance in a direct current circuit.

2

Substitute the given values into the rearranged formula and compute the current.

I = \frac{12\text{ V}}{6\ \Omega} = 2\text{ A}

.

Carrying out the division provides the magnitude of electron flow (amperage) through the load.

Key Concept

Ohm's Law formula for calculating current:

I = \frac{V}{R}

Estimated Time:40s

Question 3Question →

In a test circuit, a $1.2\text{ k}\Omega$ resistor is connected across an adjustable DC power supply. When the supply voltage is increased by $18\text{ V}$ , the current through the resistor reaches $35\text{ mA}$ . What was the initial current flowing through the resistor in milliamperes ( $\text{mA}$ )?

Show answer & explanation

Answer: 20

Answer

The initial current flowing through the resistor was

20\text{ mA}

.

Applying Ohm's Law (

I = \frac{V}{R}

), an

18\text{ V}

voltage increase across a

1.2\text{ k}\Omega

(

1{}200\ \Omega

) resistor causes a current increase of

\Delta I = \frac{18\text{ V}}{1{}200\ \Omega} = 0.015\text{ A} = 15\text{ mA}

. Subtracting this

15\text{ mA}

change from the final current of

35\text{ mA}

yields an initial current of

20\text{ mA}

.

Step-by-Step Solution

1

Convert resistance from kilohms (

k\Omega

) to ohms (

\Omega

).

R = 1.2\text{ k}\Omega = 1{}200\ \Omega

Ohm's Law calculations require standard base SI units (

V

in volts,

I

in amperes,

R

in ohms).

2

Calculate the increase in current (

\Delta I

) resulting from the

18\text{ V}

voltage increase.

\Delta I = \frac{\Delta V}{R} = \frac{18\text{ V}}{1{}200\ \Omega} = 0.015\text{ A} = 15\text{ mA}

According to Ohm's Law (

I = \frac{V}{R}

), an increase in voltage produces a directly proportional increase in current across a constant resistance.

3

Find the initial current by subtracting the current increase from the final current.

I_{\text{initial}} = 35\text{ mA} - 15\text{ mA} = 20\text{ mA}

The final current represents the sum of the initial current and the incremental current produced by the added voltage.

Key Concept

Ohm's Law defines the direct relationship between voltage and current across a constant resistance (

I = \frac{V}{R}

), meaning a change in voltage causes a proportional change in current.

Alternative Method

Calculate the final voltage first:

V_{\text{final}} = I_{\text{final}} \times R = 0.035\text{ A} \times 1{}200\ \Omega = 42\text{ V}

. Then subtract the

18\text{ V}

increase to find the initial voltage:

V_{\text{initial}} = 42\text{ V} - 18\text{ V} = 24\text{ V}

. Finally, compute the initial current:

I_{\text{initial}} = \frac{24\text{ V}}{1{}200\ \Omega} = 0.020\text{ A} = 20\text{ mA}

.

Estimated Time:50s

Question 4Question →

A direct current (DC) relay coil with a fixed resistance draws $30\text{ mA}$ when connected across an $18\text{ V}$ power supply. When the same relay coil is connected to a different DC power supply, an ammeter measures a current flow of $75\text{ mA}$ through the coil. What is the voltage of the second power supply?

7.2\text{ V}

45\text{ V}

4.5\text{ V}

75\text{ V}

Show answer & explanation

Answer: $45\text{ V}$

Answer

45\text{ V}

The correct answer is determined by using Ohm's law (

R = \frac{V}{I}

) to find the coil's fixed resistance from the initial state (

R = \frac{18\text{ V}}{0.030\text{ A}} = 600\,\Omega

) and then determining the new voltage (

V = 0.075\text{ A} \times 600\,\Omega = 45\text{ V}

).

Step-by-Step Solution

1

Convert the initial current from milliamperes to amperes and calculate the resistance of the relay coil using Ohm's law (

R = \frac{V}{I}

).

I_1 = 30\text{ mA} = 0.030\text{ A}

;

R = \frac{18\text{ V}}{0.030\text{ A}} = 600\,\Omega

The resistance of the coil remains constant regardless of the applied supply voltage.

2

Convert the second current reading to amperes and calculate the new supply voltage using Ohm's law (

V = I \times R

).

I_2 = 75\text{ mA} = 0.075\text{ A}

;

V_2 = 0.075\text{ A} \times 600\,\Omega = 45\text{ V}

Ohm's law states that the potential difference across a resistor equals current multiplied by resistance.

Key Concept

Direct proportionality between voltage and current across a fixed resistance (

V = I \times R

) and metric unit conversion.

Estimated Time:45s

Question 5Question →

An electrical technician is analyzing a perfectly ohmic heating element in a circuit. During initial operation, when an unknown voltage $V$ is applied, the element draws a current of $45 \text{ mA}$ . The technician notes that if the applied voltage is increased by exactly $500 \text{ mV}$ , the current drawn by the element increases by $2.5 \text{ mA}$ . Assuming the element's resistance remains completely constant throughout the test, what was the original applied voltage $V$ ?

9.5 V

9 V

225 V

0.9 V

Show answer & explanation

Answer: 9 V

Answer

9 V

For an ohmic component, resistance (

R

) is constant. This means the change in voltage is directly proportional to the change in current. The resistance can be found using the changes:

R = \Delta V / \Delta I

. After converting to base units,

R = 0.5 \text{ V} / 0.0025 \text{ A} = 200 \, \Omega

. Using Ohm's Law (

V = I \times R

), the original voltage is the original current (

0.045 \text{ A}

) multiplied by this resistance, resulting in

0.045 \text{ A} \times 200 \, \Omega = 9 \text{ V}

.

Step-by-Step Solution

1

Identify the relationship between the change in voltage (ΔV) and the change in current (ΔI).

R = \frac{\Delta V}{\Delta I}

For a perfectly ohmic component, the resistance is constant. This means the slope of the voltage-current relationship defines the resistance.

2

Convert the change values into standard base units (Volts and Amperes) and calculate the resistance.

\Delta V = 500 \text{ mV} = 0.5 \text{ V}

, and

\Delta I = 2.5 \text{ mA} = 0.0025 \text{ A}

.

R = \frac{0.5 \text{ V}}{0.0025 \text{ A}} = 200 \, \Omega

Standardizing metric prefixes prevents decimal shift errors before applying Ohm's Law.

3

Apply Ohm's Law to the original state to find the initial voltage.

V = I_{original} \times R = 0.045 \text{ A} \times 200 \, \Omega = 9 \text{ V}

Multiplying the originally measured current by the established component resistance yields the original voltage applied.

Key Concept

Applying Ohm's Law using proportional changes (ΔV and ΔI) while accurately managing metric prefix conversions.

Question 6Question →

An electronics technician is testing a DC bias circuit containing a fixed resistor connected to an adjustable DC power supply. When the supply voltage is set to $28\text{ V}$ , the circuit ammeter measures a current of $3.5\text{ mA}$ . To increase the current flow through the resistor to $11\text{ mA}$ , what must the power supply voltage be set to?

60\text{ V}

8.8\text{ V}

88\text{ V}

22\text{ V}

Show answer & explanation

Answer: $88\text{ V}$

Answer

The power supply voltage must be set to

88\text{ V}

.

The power supply must be set to

88\text{ V}

. First, determine the component's constant resistance:

R = \frac{28\text{ V}}{3.5\text{ mA}} = 8\text{ k}\Omega

. Next, apply Ohm's Law to find the voltage required for the target current:

V = 11\text{ mA} \times 8\text{ k}\Omega = 88\text{ V}

. Alternatively, using direct proportionality:

V_2 = 28\text{ V} \times \left(\frac{11\text{ mA}}{3.5\text{ mA}}\right) = 88\text{ V}

.

Step-by-Step Solution

1

Calculate the fixed resistance using the initial voltage and current measurements.

R = \frac{V_1}{I_1} = \frac{28\text{ V}}{3.5\text{ mA}} = \frac{28\text{ V}}{0.0035\text{ A}} = 8{}000\,\Omega = 8\text{ k}\Omega

Ohm's Law defines resistance as the ratio of voltage to current (

R = \frac{V}{I}

).

2

Calculate the new voltage required to produce

11\text{ mA}

through the

8\text{ k}\Omega

resistor.

V_2 = I_2 \times R = 0.011\text{ A} \times 8{}000\,\Omega = 88\text{ V}

Applying Ohm's Law in the form

V = I \times R

determines the potential difference needed for the desired current.

Key Concept

Ohm's Law defines the fundamental linear relationship between voltage, current, and resistance in a DC circuit (

V = I \times R

). In a circuit with constant resistance, voltage is directly proportional to current.

Alternative Method

Because resistance is constant, voltage is directly proportional to current:

V_2 = V_1 \times \frac{I_2}{I_1} = 28\text{ V} \times \frac{11\text{ mA}}{3.5\text{ mA}} = 28 \times \frac{22}{7} = 4 \times 22 = 88\text{ V}

.

Estimated Time:45s

Question 7Question →

A DC cooling fan installed in an equipment enclosure has an internal resistance of $16\ \Omega$ and draws a steady current of $1.5\text{ A}$ during normal operation. According to Ohm's law, what is the voltage drop across the fan in volts ( $\text{V}$ )?

Show answer & explanation

Answer: 24

Answer

24 V

According to Ohm's law, voltage (

V

) is found by multiplying current (

I

) by resistance (

R

). With a current of

1.5\text{ A}

and a resistance of

16\ \Omega

, the voltage is

1.5 \times 16 = 24\text{ V}

.

Step-by-Step Solution

1

Identify the known electrical quantities from the problem statement.

I = 1.5\text{ A}

and

R = 16\ \Omega

Ohm's law requires current and resistance values to calculate voltage.

2

State Ohm's law formula arranged to solve for voltage (

V

).

V = I \times R

The potential difference across a resistive element is directly proportional to the product of current and resistance.

3

Multiply the current by the resistance to find the voltage.

V = 1.5\text{ A} \times 16\ \Omega = 24\text{ V}

Performing the multiplication yields the potential difference in volts.

Key Concept

Ohm's Law (

V = I \times R

)

Estimated Time:30s

Question 8Question →

An electronics technician is testing an aircraft panel indicator circuit. When connected to a $24\text{ V}$ DC power supply, the circuit draws a steady current of $4\text{ A}$ . What is the resistance of the circuit, and what current will flow if the supply voltage is reduced to $12\text{ V}$ ?

Fill in the blanks below

According to Ohm's Law, the resistance of the circuit is

\Omega

, and when the voltage is decreased to

12\text{ V}

, the new current drawn by the circuit is

\text{A}

.

Show answer & explanation

Answer

The resistance of the circuit is

6\ \Omega

and the current under the reduced voltage is

2\text{ A}

.

Applying Ohm's Law, the resistance is found by dividing the initial voltage by the initial current (

R = \frac{24\text{ V}}{4\text{ A}} = 6\ \Omega

). Keeping this resistance constant, halving the voltage to

12\text{ V}

results in half the current (

I = \frac{12\text{ V}}{6\ \Omega} = 2\text{ A}

).

Step-by-Step Solution

1

Calculate the circuit resistance using Ohm's Law with the initial parameters (

V_1 = 24\text{ V}

,

I_1 = 4\text{ A}

).

R = \frac{V_1}{I_1} = \frac{24\text{ V}}{4\text{ A}} = 6\ \Omega

Ohm's Law states that resistance equals voltage divided by current (

R = \frac{V}{I}

).

2

Determine the new current when the voltage is adjusted to

V_2 = 12\text{ V}

across the constant

6\ \Omega

resistance.

I_2 = \frac{V_2}{R} = \frac{12\text{ V}}{6\ \Omega} = 2\text{ A}

Current is directly proportional to voltage for a fixed resistance (

I = \frac{V}{R}

).

Key Concept

Ohm's Law expresses the fundamental relationship among voltage, current, and resistance:

V = I \times R

,

I = \frac{V}{R}

, and

R = \frac{V}{I}

.

Estimated Time:45s

Question 9Question →

A benchtop DC power supply delivers $45\text{ V}$ across a fixed resistor in a test circuit. A series ammeter measures a steady current flow of $5\text{ A}$ through the component. What is the electrical resistance of the resistor?

225\ \Omega

9\ \Omega

40\ \Omega

90\ \Omega

Show answer & explanation

Answer: $9\ \Omega$

Answer

9\ \Omega

According to Ohm's Law, electrical resistance is equal to the voltage across a component divided by the current passing through it (

R = V / I

). Substituting

45\text{ V}

and

5\text{ A}

yields

R = 45 / 5 = 9\ \Omega

.

Step-by-Step Solution

1

Identify the given circuit parameters and standard Ohm's Law formula

Voltage

V = 45\text{ V}

, Current

I = 5\text{ A}

, Ohm's Law:

V = I \times R

Ohm's Law defines the relationship between potential difference, current flow, and resistance in a DC circuit.

2

Rearrange Ohm's Law to solve for resistance (

R

)

R = \frac{V}{I}

Dividing both sides of

V = I \times R

by current isolates the unknown resistance.

3

Substitute the given values into the formula and evaluate

R = \frac{45\text{ V}}{5\text{ A}} = 9\ \Omega

Dividing 45 by 5 yields the exact resistance value in ohms.

Key Concept

Ohm's Law Resistance Calculation (

R = V / I

)

Estimated Time:45s

Question 10Question →

A portable electric heater is connected to a $120\text{ V}$ direct-current power supply. If the heating element has an internal resistance of $24\ \Omega$ , what is the current flowing through the circuit?

0.2\text{ A}

5\text{ A}

50\text{ A}

2{}880\text{ A}

Show answer & explanation

Answer: $5\text{ A}$

Answer

5\text{ A}

Using Ohm's Law (

I = \frac{V}{R}

), dividing the applied voltage of

120\text{ V}

by the resistance of

24\ \Omega

yields exactly

5\text{ A}

.

Step-by-Step Solution

1

Identify the known values and state Ohm's Law formula for current.

Voltage

V = 120\text{ V}

, Resistance

R = 24\ \Omega

, Formula:

I = \frac{V}{R}

Ohm's Law states that current is directly proportional to voltage and inversely proportional to resistance.

2

Substitute the circuit values into the formula and solve for current (

I

).

I = \frac{120\text{ V}}{24\ \Omega} = 5\text{ A}

Dividing

120

by

24

computes the magnitude of current flow in amperes.

Key Concept

Ohm's Law expresses the fundamental relationship among voltage, current, and resistance (

I = V / R

).

Estimated Time:45s

Question 11Question →

A $36\text{ V}$ DC control circuit supplies power to a single heating element. An inline ammeter measures a steady current flow of $3\text{ A}$ through the circuit. What is the electrical resistance of the heating element in ohms?

Show answer & explanation

Answer: 12

Answer

12 ohms

According to Ohm's Law, resistance equals voltage divided by current (

R = \frac{V}{I}

). Dividing the source voltage of

36\text{ V}

by the current of

3\text{ A}

yields

12\ \Omega

.

Step-by-Step Solution

1

Identify the known electrical values provided in the problem

Voltage (

V

) =

36\text{ V}

, Current (

I

) =

3\text{ A}

Ohm's Law relates potential difference, current flow, and circuit resistance.

2

Rearrange Ohm's Law to express resistance in terms of voltage and current

R = \frac{V}{I}

Resistance is defined as the ratio of voltage across a component to the current flowing through it.

3

Substitute the numerical values into the equation and solve

R = \frac{36\text{ V}}{3\text{ A}} = 12\ \Omega

Dividing 36 by 3 gives the resistance directly in ohms.

Key Concept

Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance (

V = I \times R

, which rearranges to

R = \frac{V}{I}

).

Estimated Time:30s

Question 12Question →

An electric horn connected to a $12\text{ V}$ direct current (DC) automotive battery has an internal resistance of $3\ \Omega$ . What is the steady current flowing through the horn circuit? Complete the statement below.

Fill in the blanks below

According to Ohm's law, the current flowing through the horn is amperes.

Show answer & explanation

Answer

4 amperes (or 4)

According to Ohm's law, current is calculated using the formula

I = \frac{V}{R}

. Dividing the applied voltage (

12\text{ V}

) by the circuit resistance (

3\ \Omega

) gives a current of

4\text{ A}

.

Step-by-Step Solution

1

Identify the given electrical parameters from the problem statement

Voltage (

V

) =

12\text{ V}

, Resistance (

R

) =

3\ \Omega

Ohm's law relates voltage, current, and resistance in a closed DC circuit.

2

State Ohm's law rearranged to solve for current (

I

)

I = \frac{V}{R}

Current is directly proportional to voltage and inversely proportional to resistance.

3

Substitute the given numerical values into the formula and calculate

I = \frac{12\text{ V}}{3\ \Omega} = 4\text{ A}

Dividing

12

volts by

3

ohms yields

4

amperes.

Key Concept

Ohm's Law states that current (

I

) equals voltage (

V

) divided by resistance (

R

).

Estimated Time:45s

Question 13Question →

A technician measures a steady current of $50\text{ mA}$ flowing through a $120\ \Omega$ fixed resistor in a signal conditioning module. What is the voltage drop across the resistor?

2.4\text{ V}

6\text{ V}

6{}000\text{ V}

0.6\text{ V}

Show answer & explanation

Answer: $6\text{ V}$

Answer

6\text{ V}

According to Ohm's law, the voltage drop across a component is determined by multiplying current by resistance (

V = I \times R

). Converting

50\text{ mA}

to

0.05\text{ A}

and multiplying by

120\ \Omega

gives

6\text{ V}

.

Step-by-Step Solution

1

Convert the current from milliamperes (mA) to amperes (A).

50\text{ mA} = 0.05\text{ A}

Standard electrical formulas require current in amperes.

2

Apply Ohm's law formula for voltage (

V = I \times R

).

V = 0.05\text{ A} \times 120\ \Omega = 6\text{ V}

Voltage across a resistor equals the product of current and resistance.

Key Concept

Ohm's Law states that voltage is equal to current multiplied by resistance (

V = I \times R

).

Estimated Time:45s

Question 14Question →

In an auxiliary radio circuit, a direct-current source applies $24\text{ V}$ across a fixed resistor, producing a measured current flow of $8\text{ mA}$ . What is the resistance of the component?

3\ \Omega

192\ \Omega

300\ \Omega

3{}000\ \Omega

Show answer & explanation

Answer: $3{}000\ \Omega$

Answer

3{}000\ \Omega

Applying Ohm's Law (

R = \frac{V}{I}

) with the current converted to amperes (

8\text{ mA} = 0.008\text{ A}

) gives

\frac{24\text{ V}}{0.008\text{ A}} = 3{}000\ \Omega

.

Step-by-Step Solution

1

Convert the current from milliamperes (mA) to base amperes (A)

8\text{ mA} = 8 \times 10^{-3}\text{ A} = 0.008\text{ A}

Ohm's Law calculations require current in base units of amperes.

2

Apply Ohm's Law to solve for resistance (

R

)

R = \frac{V}{I} = \frac{24\text{ V}}{0.008\text{ A}} = 3{}000\ \Omega

Resistance equals voltage divided by current.

Key Concept

Ohm's Law defines the direct relationship between voltage, current, and resistance in a DC circuit (

R = \frac{V}{I}

).

Estimated Time:45s

Question 15Question →

An electromagnetic security gate lock operates on an $18\text{ V}$ direct-current (DC) power source. When fully energized, the lock draws a steady current of $250\text{ mA}$ . What is the electrical resistance of the lock in ohms ( $\Omega$ )?

Show answer & explanation

Answer: 72

Answer

The electrical resistance of the electromagnetic lock is

72\ \Omega

.

According to Ohm's Law (

V = I \times R

), resistance is found by dividing the potential difference by the current (

R = \frac{V}{I}

). Converting

250\text{ mA}

to

0.25\text{ A}

and dividing

18\text{ V}

by

0.25\text{ A}

yields exactly

72\ \Omega

.

Step-by-Step Solution

1

Convert the current measurement from milliamperes (

\text{mA}

) to amperes (

\text{A}

).

I = 250\text{ mA} = 0.25\text{ A}

Ohm's Law calculations require current in base SI units (amperes) to yield resistance in ohms.

2

Rearrange Ohm's Law (

V = I \times R

) to isolate resistance (

R

).

R = \frac{V}{I}

Resistance is equal to the applied electromotive force (voltage) divided by the resulting current flow.

3

Substitute the given voltage and converted current into the formula and solve.

R = \frac{18\text{ V}}{0.25\text{ A}} = 72\ \Omega

Dividing

18\text{ V}

by

0.25\text{ A}

gives the total circuit resistance in ohms.

Key Concept

Ohm's Law states that resistance (

R

) equals voltage (

V

) divided by current (

I

), represented by the formula

R = \frac{V}{I}

.

Estimated Time:45s

Question 16Question →

A telemetry sensor on an unmanned aerial vehicle is connected to a $15\text{ V}$ direct-current (DC) power supply. If the sensor circuit has an effective resistance of $2.5\text{ k}\Omega$ , what is the steady current flowing through the circuit in milliamperes ( $\text{mA}$ )?

37.5\text{ mA}

6\text{ mA}

60\text{ mA}

167\text{ mA}

Show answer & explanation

Answer: $6\text{ mA}$

Answer

The steady current flowing through the sensor circuit is

6\text{ mA}

.

According to Ohm's Law, current equals voltage divided by resistance (

I = \frac{V}{R}

). Converting

2.5\text{ k}\Omega

to

2{}500\ \Omega

gives

I = \frac{15\text{ V}}{2{}500\ \Omega} = 0.006\text{ A}

, which equals

6\text{ mA}

.

Step-by-Step Solution

1

Convert the resistance value from kilohms (

\text{k}\Omega

) to base ohms (

\Omega

).

R = 2.5\text{ k}\Omega = 2.5 \times 10^3\ \Omega = 2{}500\ \Omega

Ohm's Law calculations require base electrical units (volts, amperes, and ohms).

2

Apply Ohm's Law to solve for current in amperes (

I = \frac{V}{R}

).

I = \frac{15\text{ V}}{2{}500\ \Omega} = 0.006\text{ A}

Current is directly proportional to voltage and inversely proportional to resistance.

3

Convert the resulting current from amperes (

\text{A}

) to milliamperes (

\text{mA}

).

I = 0.006\text{ A} \times 1{}000\text{ mA/A} = 6\text{ mA}

The question asks for the final answer in milliamperes.

Key Concept

Ohm's Law defines the relationship between voltage, current, and resistance (

I = \frac{V}{R}

).

Estimated Time:45s

Question 17Question →

An avionics technician is analyzing a direct-current (DC) subassembly with an applied voltage of $36\text{ V}$ across a load resistor rated at $1.8\text{ k}\Omega$ . What is the resistance in ohms and the resulting current in milliamperes? Fill in the blanks below to complete the circuit analysis.

Fill in the blanks below

The total resistance of the load is

\Omega

, and the steady current flowing through the circuit is

\text{mA}

.

Show answer & explanation

Answer

The resistance is 1800 Ω and the current is 20 mA.

Converting

1.8\text{ k}\Omega

to base units gives

1800\ \Omega

. Dividing the applied voltage of

36\text{ V}

by

1800\ \Omega

yields

0.02\text{ A}

, which corresponds to

20\text{ mA}

.

Step-by-Step Solution

1

Convert the load resistance from kilohms (kΩ) to ohms (Ω)

R = 1.8\text{ k}\Omega = 1.8 \times 1000\ \Omega = 1800\ \Omega

Standard electrical calculations using Ohm's Law require base units of ohms, volts, and amperes.

2

Apply Ohm's Law (

I = \frac{V}{R}

) to calculate the circuit current in amperes

I = \frac{36\text{ V}}{1800\ \Omega} = 0.02\text{ A}

Current is directly proportional to voltage and inversely proportional to resistance.

3

Convert the current from amperes (A) to milliamperes (mA)

I = 0.02\text{ A} \times 1000\text{ mA/A} = 20\text{ mA}

The required unit for the current blank is milliamperes.

Key Concept

Ohm's Law (

I = \frac{V}{R}

) and metric prefix conversions (kilo- and milli-).

Estimated Time:45s

Question 18Question →

A technician is testing a direct-current (DC) indicator lamp assembly in an armored vehicle. The lamp is connected to a $24\text{ V}$ power supply and draws a steady current of $75\text{ mA}$ . What is the total electrical resistance of the lamp assembly?

0.32\ \Omega

1.8\ \Omega

320\ \Omega

1,800\ \Omega

Show answer & explanation

Answer: $320\ \Omega$

Answer

The total resistance of the lamp assembly is

320\ \Omega

.

According to Ohm's Law (

V = I \times R

), resistance equals voltage divided by current (

R = \frac{V}{I}

). Converting

75\text{ mA}

to

0.075\text{ A}

and dividing

24\text{ V}

by

0.075\text{ A}

yields

320\ \Omega

.

Step-by-Step Solution

1

Convert the measured current from milliamperes (

\text{mA}

) to base amperes (

\text{A}

).

I = 75\text{ mA} = \frac{75}{1000}\text{ A} = 0.075\text{ A}

Ohm's Law calculations require standard SI units (amperes) to yield resistance in ohms.

2

Rearrange Ohm's Law (

V = I \times R

) to solve for resistance (

R = \frac{V}{I}

) and substitute the known values.

R = \frac{24\text{ V}}{0.075\text{ A}} = 320\ \Omega

Dividing the applied voltage by the circuit current gives the total resistance.

Key Concept

Ohm's Law defines the relationship between voltage, current, and resistance (

V = I \times R

, rearranged as

R = \frac{V}{I}

). Current must always be converted to base amperes before computing resistance.

Estimated Time:45s

Question 19Question →

An aircraft instrument panel illumination circuit is connected to a $28\text{ V}$ direct-current (DC) power source. A multimeter measures a steady current flow of $350\text{ mA}$ through the circuit. What is the total electrical resistance of the circuit in ohms ( $\Omega$ )?

Show answer & explanation

Answer: 80

Answer

The total electrical resistance of the circuit is

80\ \Omega

.

According to Ohm's Law, resistance equals voltage divided by current (

R = \frac{V}{I}

). Converting

350\text{ mA}

to amperes yields

0.35\text{ A}

. Dividing

28\text{ V}

by

0.35\text{ A}

gives the correct resistance of

80\ \Omega

.

Step-by-Step Solution

1

Convert the current from milliamperes to amperes

I = 350\text{ mA} = 0.35\text{ A}

Ohm's Law calculations require current to be expressed in standard amperes.

2

Apply Ohm's Law formula solved for resistance

R = \frac{V}{I} = \frac{28\text{ V}}{0.35\text{ A}} = 80\ \Omega

Dividing the applied electromotive force by the current flow yields total circuit resistance.

Key Concept

Calculating resistance using Ohm's Law (

R = \frac{V}{I}

) with metric prefix conversion (

1\text{ A} = 1{}000\text{ mA}

).

Estimated Time:45s

Question 20Question →

A technician is servicing a communications shelter ventilation fan controller that operates on a $48\text{ V}$ direct-current (DC) power supply. A diagnostic test shows that the control circuit's primary sensing resistor has a resistance of $1.2\text{ k}\Omega$ . What is the current flowing through this resistor?

25\text{ mA}

40\text{ mA}

400\text{ mA}

57.6\text{ mA}

Show answer & explanation

Answer: $40\text{ mA}$

Answer

40\text{ mA}

According to Ohm's Law, current is calculated by dividing voltage by resistance (

I = \frac{V}{R}

). First converting

1.2\text{ k}\Omega

to

1200\ \Omega

gives

I = \frac{48\text{ V}}{1200\ \Omega} = 0.04\text{ A}

, which is equivalent to

40\text{ mA}

.

Step-by-Step Solution

1

Convert the resistance value from kilohms (

\text{k}\Omega

) to base ohms (

\Omega

).

R = 1.2\text{ k}\Omega = 1.2 \times 1000\ \Omega = 1200\ \Omega

Standard electrical calculations using Ohm's Law require base units of volts, amperes, and ohms.

2

Apply Ohm's Law (

I = \frac{V}{R}

) to solve for the circuit current.

I = \frac{48\text{ V}}{1200\ \Omega} = 0.04\text{ A}

Current equals voltage divided by resistance.

3

Convert the current in amperes to milliamperes (

\text{mA}

).

0.04\text{ A} \times 1000\text{ mA/A} = 40\text{ mA}

The answer choices are expressed in milliamperes.

Key Concept

Ohm's Law (

I = \frac{V}{R}

) and metric prefix conversions

Estimated Time:45s

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