Practice Resistance in Physics

Use these practice problems to test your method after reviewing the concept explanation and worked examples.

Worksheet PDF Free Answer-key PDF Family

Quick Recap

A measure of how strongly a material opposes electric current, measured in ohms ( $\Omega$ ) — higher resistance means less current for a given voltage.

Resistance is like friction for electricity — a narrow pipe resists water flow more than a wide one.

Showing a random 20 of 50 problems.

Example 1

challenge

Twelve identical

1 \text{ }\Omega

resistors are arranged along the edges of a cube. Find the resistance between two opposite corners (body diagonal).

Example 2

medium

A material has resistivity

2\times10^{-8}\,\Omega\cdot

m. A wire is

4

m long with cross-section

2\times10^{-6}

^2

. Find its resistance.

Example 3

easy

If voltage stays constant and resistance triples, the current becomes ___.

Example 4

hard

Find the equivalent resistance between A and B:

R_1 = 4 \text{ }\Omega

in series with the parallel combination of

R_2 = 6 \text{ }\Omega

and (

R_3 = 3 \text{ }\Omega

in series with

R_4 = 3 \text{ }\Omega

Example 5

medium

Two resistors

12 \text{ }\Omega

and

4 \text{ }\Omega

are in parallel. Find the equivalent resistance.

R_eq

Example 6

medium

Three identical

9 \text{ }\Omega

resistors are connected in parallel. Find

R_{eq}

Example 7

medium

A heater draws

10 \text{ A}

from a

220 \text{ V}

supply. Find its resistance.

Example 8

easy

What is the SI unit of resistance?

Example 9

easy

What is the SI unit of resistance?

Example 10

challenge

4\,\Omega

resistor is in series with a parallel combination of

6\,\Omega

and

12\,\Omega

. Find the total resistance.

R_p = 4 Ω; R_total

Example 11

medium

A wire has resistance

R = \rho \frac{L}{A}

. If you replace a wire with one that is twice as long and has three times the cross-sectional area (same material), how does the resistance change?

Example 12

medium

A wire has resistance

6\,\Omega

. It is stretched to twice its length (area halves, volume constant). What is the new resistance?

Example 13

easy

20 \text{ }\Omega

resistor and

30 \text{ }\Omega

resistor are in series. The current through the

20 \text{ }\Omega

resistor is what fraction of the current through the

30 \text{ }\Omega

resistor?

Example 14

easy

Two identical resistors are connected in parallel. The equivalent resistance is ___ that of a single resistor.

Example 15

easy

A resistor carries

2 \text{ A}

of current when

10 \text{ V}

is applied across it. What is the resistance?

Find the resistance of the single resistor

Example 16

easy

A bulb labeled

60 \text{ W}, 120 \text{ V}

has what resistance when operating?

Example 17

easy

What is the difference between resistance and resistivity?

Example 18

easy

A resistor has

12

V across it and

3

A through it. What is its resistance?

R = V/I

Example 19

medium

A wire has length

2 \text{ m}

, cross-sectional area

1 \times 10^{-6} \text{ m}^2

, and resistivity

\rho = 1.7 \times 10^{-8} \text{ } \Omega \cdot \text{m}

(copper). What is its resistance?

Example 20

medium

Two resistors

6\,\Omega

and

3\,\Omega

are in parallel. Find the total resistance.

1/R

← Back to Resistance Worked Examples Formula Explained

Related Concepts

Electric Current Voltage Ohm's Law Series Circuit Parallel Circuit