Electromagetism Review

Four SI units are as follows:

P. volt second^-1

Q. volt second

R. tesla metre^-2

S. tesla metre²

Which pair of units are equivalent to the weber?

• P and R

• Q and S

• P and S

• Q and R

How are the units of magnetic flux and that of magnetic flux density related?

• 1 Wb = 1 T m^-3

• 1 Wb = 1 T m^-2

• 1 Wb = 1 T m²

• 1 Wb = 1 T m³

Which of the following best describes one weber?

• The flux density of a field in which a conductor of length 1 m carrying a current of 1 A at right-angles to the field experiences a magnetic force of 1 N.

• The flux density of a field in which a conductor of length 1 m carrying a current of 1 A parallel to the field experiences a force of 1 N.

• The magnetic flux passing through a plane surface of 1 m² placed normal to a uniform magnetic field of flux density 1 T.

• The magnetic flux passing through a plane surface of 1 m² placed parallel to a uniform magnetic field of flux density 1 T.

Which of the following best describes the magnetic flux through a plane surface in a uniform magnetic field?

• the product of the flux density and the component area normal to the field.

• the product of the flux density and the component area parallel to the field.

• the flux density per unit area normal to the field.

• the flux density per unit area parallel to the field.

Which of the following best describes the direction of an induced current according to Lenz's law?

• a direction that is parallel to the change that induced it.

• a direction that is independent of the change that induced it.

• a direction that produces effects to oppose the change that induced it.

• a direction that produces effects to complement the change that induced it.

A metal bar is placed in a horizontal position within a region of vertically directed uniform magnetic field B. If the bar is rotated at an angular velocity ω about a vertical axis through its centre, what would be the e.m.f. between the two ends of the bar?

• It is zero.

• It is proportional to the product B ω

• It is proportional to the product B ω²

• It is proportional to the product B² ω²

A coil of N turns and an area A is placed in a uniform magnetic field of flux density B, and the axis of the coil makes an angle θ with the field. What is the flux linkage of the coil?

• B A N cosθ

• B A N sinθ

• B N cosθ / A

• B N sinθ / A

The variation with time t of the flux density B of a magnetic field is as shown. An e.m.f. is induced in a wire subjected to the changing field.

At which of the following values of t is the magnitude of the induced e.m.f. a maximum?

• 1 ms

• 2 ms

• 3 ms

• 4 ms

When the North pole of a bar magnet is moved into the end of a coil of wire, as shown, the maximum deflection of the meter needle is 10 units to the left.

If the South pole of the magnet is then moved into the other end of the coil at twice the speed, what is the maximum deflection of the meter needle?

• less than 10 units to the left

• less than 10 units to the right

• more than 10 units to the left

• more than 10 units to the right

Which of the following does not involve the application of electromagnetic induction?

• A generator

• A bicycle dynamo

• A transformer

• An operational amplifier