Practice Magnetic 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 vector field around magnets and moving charges that exerts force on other moving charges and magnetic materials.

Moving charges create a swirling force field around them. This field can push on other moving charges or magnets.

Showing a random 20 of 50 problems.

Example 1

hard
A coil of 5050 turns and area 0.02 m20.02\text{ m}^2 sits in a field that changes from 0.4 T0.4\text{ T} to 00 in 0.1 s0.1\text{ s}. Find the induced EMF magnitude.

Example 2

medium
Field B=0.6B=0.6 T through area A=2A=2 m2^2 at θ=60°\theta=60° from the normal. Find the flux. (cos⁡60°=0.5\cos60°=0.5.)

Example 3

hard
An electron (q=−1.6×10−19 C,  m=9.11×10−31 kgq = -1.6\times10^{-19}\text{ C},\; m = 9.11\times10^{-31}\text{ kg}) moves at 4×106 m/s4\times10^6\text{ m/s} perpendicular to a 0.2 T0.2\text{ T} field. Find the radius of its circular path.

Example 4

medium
Two parallel wires each carry current and create fields. The field at a point from one wire is 0.30.3 T east, from the other 0.40.4 T north. Find the net field magnitude.

Example 5

easy
A wire carries 33 A over 22 m in a 0.20.2 T field, perpendicular. Find the force.

Example 6

medium
A proton (q=1.6×10−19 Cq = 1.6 \times 10^{-19} \text{ C}) moves at 3×106 m/s3 \times 10^6 \text{ m/s} perpendicular to a magnetic field of 0.5 T0.5 \text{ T}. What force does it experience?

Example 7

challenge
A charged particle enters a uniform field with a velocity that has both parallel and perpendicular components. Describe the resulting path.

Example 8

medium
Earth's magnetic field at the surface is roughly 5×10−5 T5\times10^{-5}\text{ T}. Express in milligauss (use 1 T=104 G1\text{ T} = 10^4\text{ G}, 1 G=103 mG1\text{ G} = 10^3\text{ mG}).

Example 9

easy
Do magnetic field lines start and stop, or form closed loops?

Example 10

medium
What is the magnetic force on a charged particle that moves parallel to the field?

Example 11

easy
Is magnetic field a vector or a scalar?

Example 12

hard
Why do magnetic field lines never cross?

Example 13

medium
A wire feels maximum force 88 N when perpendicular to a field. What force does it feel at 30°30°? (sin⁡30°=0.5\sin30°=0.5.)

Example 14

easy
In a 0.50.5 T field, a wire carries 22 A over length 11 m perpendicular to the field. Find the force. (sin⁡90°=1\sin90°=1.)

Example 15

challenge
Two long parallel wires 0.10.1 m apart carry currents that produce a field of 4×10−64\times10^{-6} T from one wire at the other. Each wire is 22 m long carrying 22 A. Find the force between them.

Example 16

easy
Magnetic field lines exit which pole of a permanent magnet?

Example 17

challenge
A charge q=1q=1 C, mass m=2m=2 kg, moves at v=4v=4 m/s perpendicular to B=0.5B=0.5 T. Find the radius of its circular path.

Example 18

medium
A 2 m2\text{ m} wire makes a 30°30° angle with a 0.5 T0.5\text{ T} field and carries 4 A4\text{ A}. Find the force on the wire.

Example 19

medium
An electron moves at 2×107 m/s2 \times 10^7 \text{ m/s} at 30°30° to a 0.1 T0.1 \text{ T} magnetic field. What is the magnetic force on the electron? (∣qe∣=1.6×10−19 C|q_e| = 1.6 \times 10^{-19} \text{ C})

Example 20

hard
A proton (q=1.6×10−19 Cq = 1.6 \times 10^{-19} \text{ C}, m=1.67×10−27 kgm = 1.67 \times 10^{-27} \text{ kg}) enters a uniform magnetic field of 0.2 T0.2 \text{ T} at 90°90° with a speed of 5×106 m/s5 \times 10^6 \text{ m/s}. Calculate: (a) the magnetic force, (b) the radius of its circular path.
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