Practice Electric Current in Physics

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

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Quick Recap

Electric current is the rate at which electric charge flows past a point in a circuit or conductor.

Current is like the flow rate of water in a pipe — how much charge passes a point each second.

Showing a random 20 of 50 problems.

Example 1

challenge

A circuit has three parallel branches sharing

12\ \text{A}

. Branch 1 carries twice the current of branch 2, and branch 3 carries the same as branch 2. Find each branch current.

Example 2

medium

A current of

1.5

A flows for

40

s. How much charge passes?

Example 3

medium

A phone charger delivers a steady current of

2.0 \text{ A}

for

30 \text{ minutes}

. How much total electric charge flows through the cable?

Example 4

medium

A 5 A current flows through a wire. A student says the current is smaller after the bulb. Is this correct, and why?

Example 5

easy

Convert

750\ \text{mA}

to amperes.

Example 6

easy

A current of

1\ \text{A}

equals how many coulombs per second?

Example 7

hard

A circuit branch carries current

I(t) = 2t\ \text{A}

(with

t

in seconds) from

t=0

t=5\ \text{s}

. Find the total charge passing in that interval.

Example 8

hard

In a circuit,

4.0\ \text{A}

flows for

30\ \text{s}

, then

0\ \text{A}

for

30\ \text{s}

, then

2.0\ \text{A}

for

60\ \text{s}

. Find the average current over the full

2

minutes.

Example 9

medium

A USB-C laptop charger delivers a steady

3.0\ \text{A}

for

45\ \text{minutes}

. How much charge flows through the cable?

Example 10

medium

A car battery delivers

50\ \text{A}

to a starter motor for

3\ \text{s}

. How much charge passes?

Example 11

medium

A student measures

300\ \text{mA}

entering a bulb and reports

250\ \text{mA}

leaving it. Is this physically possible? Briefly explain.

Example 12

easy

Does the same current that enters a resistor leave it, or is current 'used up'?

Example 13

easy

Two points in a circuit pass

6

C and

6

C in the same second. Is the current the same at both?

Example 14

medium

At a junction,

7

A flows in and one branch carries

4

A out. What current leaves the other branch?

Example 15

easy

True or false: at a junction in a circuit, the sum of currents in equals the sum of currents out.

Example 16

challenge

A junction has three branches:

5

A enters,

2

A leaves one branch, and the third branch's direction is unknown. If the second branch is measured at

6

A leaving, what is the third branch current and direction?

Example 17

hard

A single AA cell delivers

40\ \text{mA}

for

25\ \text{hours}

before dying. How much total charge did it provide?

Example 18

medium

A wire carries

4\ \text{A}

for

5\ \text{minutes}

. How many electrons pass through?

Example 19

easy

Convert

500

mA to amperes.

Example 20

medium

A current of

250\ \text{mA}

flows for

4\ \text{minutes}

. How much charge passes?

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Related Concepts

Electric Charge Voltage Resistance Ohm's Law