Science: Magnetic Fields and Electromagnetic Induction Worksheet

Question 1

Describe the magnetic field around a straight wire carrying an electric current. Include the shape and direction of the field lines.

Accepted Answer

The magnetic field forms concentric circles around the wire. The direction of the field lines is found with the right-hand rule: if the thumb points in the direction of the current, the curled fingers show the direction of the magnetic field.

Question 2

A student moves the north pole of a bar magnet toward a coil of wire. Explain what happens to the magnetic flux through the coil and whether an induced current is produced.

Accepted Answer

As the magnet moves toward the coil, the magnetic flux through the coil increases. Because the flux is changing, an induced current is produced in the coil.

Question 3

State Faraday's law of electromagnetic induction in words.

Accepted Answer

Faraday's law states that a changing magnetic flux through a loop or coil induces an electromotive force. The greater the rate of change of magnetic flux, the greater the induced electromotive force.

Question 4

A coil has 200 turns. The magnetic flux through each turn changes from 0.10 weber to 0.04 weber in 0.20 second. Find the magnitude of the induced electromotive force.

Accepted Answer

The magnitude of the induced electromotive force is 60 volts. Using Faraday's law, emf = N times the change in flux divided by time = 200 times 0.06 divided by 0.20 = 60 V.

Question 5

Explain Lenz's law and how it determines the direction of induced current.

Accepted Answer

Lenz's law states that the induced current flows in the direction that creates a magnetic field opposing the change in magnetic flux that caused it. This means the induced current acts to resist the increase or decrease in flux.

Question 6

A charged particle moves perpendicular to a uniform magnetic field. What kind of path does it follow, and why?

Accepted Answer

The particle follows a circular path if its speed stays constant. The magnetic force is always perpendicular to the velocity, so it changes the direction of motion without changing the particle's speed.

Question 7

Write the equation for the magnetic force on a moving charge and define each variable.

Accepted Answer

The magnetic force is given by F = qvB sin(theta). In this equation, F is magnetic force, q is charge, v is speed, B is magnetic field strength, and theta is the angle between the velocity and the magnetic field.

Question 8

A wire 0.50 meter long carries a current of 3.0 ampere perpendicular to a magnetic field of 0.40 tesla. Calculate the magnetic force on the wire.

Accepted Answer

The magnetic force on the wire is 0.60 newton. Using F = BIL sin(theta) and sin(90 degrees) = 1, F = 0.40 times 3.0 times 0.50 = 0.60 N.

Question 9

Compare a permanent magnet and an electromagnet. Give one advantage of an electromagnet.

Accepted Answer

A permanent magnet produces a magnetic field without an electric current, while an electromagnet produces a magnetic field when current flows through a coil. One advantage of an electromagnet is that its strength can be changed by changing the current or number of turns.

Question 10

A loop of wire is stationary in a constant magnetic field. Will an induced electromotive force be produced? Explain.

Accepted Answer

No induced electromotive force is produced if the magnetic flux through the loop stays constant. Electromagnetic induction requires a change in magnetic flux, not just the presence of a magnetic field.

Question 11

List two ways to increase the induced electromotive force in a coil.

Accepted Answer

One way is to increase the rate of change of magnetic flux, such as moving the magnet faster. Another way is to increase the number of turns in the coil.

Question 12

Explain how a simple electric generator uses electromagnetic induction to produce electrical energy.

Accepted Answer

A simple electric generator rotates a coil in a magnetic field, or rotates a magnet near a coil, so the magnetic flux changes continuously. This changing flux induces an electromotive force and produces an electric current in the circuit.

Science: Magnetic Fields and Electromagnetic Induction

Science: Magnetic Fields and Electromagnetic Induction

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