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Question

Difficulty: EasyOhm's Law

A benchtop DC power supply delivers 45 V45\text{ V} across a fixed resistor in a test circuit. A series ammeter measures a steady current flow of 5 A5\text{ A} through the component. What is the electrical resistance of the resistor?

  1. A
    225 Ω225\ \Omega
  2. 9 Ω9\ \OmegaAnswer
  3. C
    40 Ω40\ \Omega
  4. D
    90 Ω90\ \Omega

Answer

9 Ω9\ \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/IR = V / I). Substituting 45 V45\text{ V} and 5 A5\text{ A} yields R=45/5=9 ΩR = 45 / 5 = 9\ \Omega.

Step-by-Step Solution

1
Identify the given circuit parameters and standard Ohm's Law formula
Voltage V=45 VV = 45\text{ V}, Current I=5 AI = 5\text{ A}, Ohm's Law: V=I×RV = 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 (RR)
R=VIR = \frac{V}{I}
Dividing both sides of V=I×RV = I \times R by current isolates the unknown resistance.
3
Substitute the given values into the formula and evaluate
R=45 V5 A=9 ΩR = \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/IR = V / I)
Estimated Time:45s
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Topics

Ohm's Law

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