An electronics technician evaluates four direct-current (DC) circuit devices under steady-… — Armed Services Vocational Aptitude Battery (ASVAB)

An electronics technician evaluates four direct-current (DC) circuit devices under steady-state conditions. Match each electrical device and operating parameter on the left with its correct calculated electrical power dissipation on the right.

An instrument panel backlight operating at $12\text{ V}$ and drawing a steady current of $0.5\text{ A}$ $6\text{ W}$
A radio-frequency dummy load resistor of $50\ \Omega$ carrying a direct current of $0.4\text{ A}$ $8\text{ W}$
A defroster heating element with a resistance of $300\ \Omega$ connected across a $60\text{ V}$ power supply $12\text{ W}$
A high-voltage bleeder resistor of $4\text{ k}\Omega$ connected across a $100\text{ V}$ potential $2.5\text{ W}$

Cevap

The backlight (

12\text{ V}, 0.5\text{ A}

) matches

6\text{ W}

; the dummy load (

50\ \Omega, 0.4\text{ A}

) matches

8\text{ W}

; the defroster element (

60\text{ V}, 300\ \Omega

) matches

12\text{ W}

; and the bleeder resistor (

4\text{ k}\Omega, 100\text{ V}

) matches

2.5\text{ W}

Each load correctly maps to its power calculation derived from Watt's Law formulas (

P = V \times I

P = I^2 \times R

, and

P = \frac{V^2}{R}

) with proper unit conversions.

Adım Adım Çözüm

Calculate the power of the instrument panel backlight using known voltage and current.

P = V \times I = 12\text{ V} \times 0.5\text{ A} = 6\text{ W}

When voltage (

V

) and current (

I

) are provided, the direct formula for electrical power is

P = V \times I

Calculate the power of the dummy load resistor using known current and resistance.

P = I^2 \times R = (0.4\text{ A})^2 \times 50\ \Omega = 0.16 \times 50 = 8\text{ W}

When current (

I

) and resistance (

R

) are known, substitute Ohm's Law (

V = I \times R

) into Watt's Law to get

P = I^2 \times R

Calculate the power of the defroster element using known voltage and resistance.

P = \frac{V^2}{R} = \frac{(60\text{ V})^2}{300\ \Omega} = \frac{3600}{300} = 12\text{ W}

When voltage (

V

) and resistance (

R

) are known, substitute

I = \frac{V}{R}

into Watt's Law to get

P = \frac{V^2}{R}

Convert the bleeder resistance from kilo-ohms to ohms and calculate its power dissipation.

R = 4\text{ k}\Omega = 4000\ \Omega

, then

P = \frac{V^2}{R} = \frac{(100\text{ V})^2}{4000\ \Omega} = \frac{10000}{4000} = 2.5\text{ W}

Metric prefixes must be converted to base units before applying Watt's Law formulas.

Anahtar Kavram

Electrical power in direct-current circuits is calculated using Watt's Law variations:

P = V \times I

P = I^2 \times R

, and

P = \frac{V^2}{R}

, depending on which two electrical parameters are known.

Tahmini Süre:1m 15s

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