Practice Electric Field in Physics

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

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Quick Recap

A region around a charged object where other charges experience a force. Measured in newtons per coulomb (N/C) or volts per meter (V/m).

Every charge creates an invisible 'force zone' around it. Another charge entering this zone feels a push or pull without touching anything.

Showing a random 20 of 50 problems.

Example 1

easy

A test charge of

2 \text{ C}

feels a force of

10 \text{ N}

at a point. What is the electric field there?

Example 2

challenge

On the line joining

+9\ \mu\text{C}

x=0

and

-1\ \mu\text{C}

x=2\ \text{m}

, where does the net field vanish? (Search outside the segment.)

Example 3

medium

Find the field

E

at the surface of a sphere of radius

0.10\ \text{m}

carrying

1.0\ \mu\text{C}

of charge. Use

k = 9\times10^9

Example 4

medium

Charges

+4 \text{ C}

x=0

and

+4 \text{ C}

x=4 \text{ m}

. Find the field at

x=2 \text{ m}

Example 5

easy

A point charge gives

E = 20 \text{ N/C}

r = 3 \text{ m}

. What is

E

r = 6 \text{ m}

Example 6

easy

Which way does the electric field point near a positive point charge?

Example 7

easy

Field lines from a negative point charge point ____ the charge.

Example 8

easy

A point charge

Q = 4 \text{ C}

. Find the field magnitude at

r = 2 \text{ m}

. Use

k = 9\times10^9

Example 9

easy

If the distance from a point charge doubles, the field becomes ____ as strong.

Example 10

medium

Two charges,

+3 \text{ C}

x=0

and

+3 \text{ C}

x=4 \text{ m}

. What is the field magnitude at the midpoint

x=2 \text{ m}

Example 11

easy

A charge

Q = 1 \text{ C}

at distance

r = 1 \text{ m}

. Find

E

. Use

k = 9\times10^9

Example 12

easy

What are the units of electric field?

Example 13

hard

Q

triples and

r

halves, by what factor does the field of a point charge change?

Example 14

hard

Two point charges are placed on the x-axis:

q_1 = +3 \times 10^{-6} \text{ C}

x = 0

and

q_2 = +3 \times 10^{-6} \text{ C}

x = 0.4 \text{ m}

. Find the electric field at the midpoint (

x = 0.2 \text{ m}

). Use

k = 9 \times 10^9

Example 15

medium

Field

E_1 = 300\ \text{N/C}

points east and

E_2 = 400\ \text{N/C}

points north at a point. Find the magnitude of the net field.

Fields E₁ = 300 N/C (east) and E₂ = 400 N/C (north) combine by vector addition to give E_net = 500 N/C.

Example 16

medium

A uniform field of

500 \text{ N/C}

accelerates a

+2 \text{ C}

charge. Find the force.

A +2 C charge accelerated by a 500 N/C uniform field; the electric force is F

Example 17

hard

A point charge

+Q

produces

E = 100\ \text{N/C}

r = 2\ \text{m}

. What is

E

r = 5\ \text{m}

Example 18

medium

Charge

+2 \text{ C}

at origin. Find the field at

r = 3 \text{ m}

. Use

k=9\times10^9

Example 19

easy

4\ \text{C}

charge feels a force of

20\ \text{N}

at a point. What is the electric field at that point?

Example 20

challenge

Three charges

+q

sit at the vertices of an equilateral triangle of side

a

. Find the magnitude of the field at the centroid.

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Related Concepts

Electric Charge Force Coulomb's Law Electric Potential Magnetic Field