Question

Stu wanted to calculate the resistance of a light bulb connected to a 4.0-V battery, with a resulting current of 0.5 A. He used the formula R = VI and obtained an answer of 2 . Was Stu’s answer correct? How do you know?

Answer 1

Answer: no, Stu's answer was incorrect.

Explanation:

The correct formula that relates current, resistance and voltage in a circuit is given by Ohm's law:

$V=RI$

or

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

where

V is the voltage in the circuit

I is the current

R is the resistance

In this circuit, the voltage is V=4.0 V, and the current is I=0.5 A, therefore the resistance of the circuit is

$R=\frac{V}{I}=\frac{4.0 V}{0.5 A}=8 \Omega$

Answer 2

Sample Response: Stu's answer was incorrect. According to Ohm's law, R = V/I. This is the equation that should be used to obtain the correct answer, which is 8 ohms.