Electromagnetism – Formal Homework 1

  1. A wind speed meter is designed as shown.

Air blows across the propellercausing the magnet to rotate. A voltage is induced

acrossthe coil.Which of the following changes willproduce an increase in the

inducedvoltage? (1)

  1. Replacing the magnet with one ofgreater field strength.
  2. Spinning the propeller faster.
  3. Reducing the number of turns onthe coil.
  1. I only
  2. I and II only
  3. I and III only
  4. II and III only
  5. I, II and III

2.The diagram shows a model bicycledynamo.

When the rotor is turned the magnetrotates, inducing a voltage in the coil.

The induced voltage can be decreasedby (1)

  1. increasing the number of turnson the coil
  2. decreasing the number of turnson the coil
  3. using a stronger magnet
  4. turning the rotor faster
  5. reversing the direction ofrotation of the magnet.
  1. When a magnet is pushed into orpulled out of a coil of wire, a voltage

is induced across the ends of the coil. (1)

Which of the following produces the greatest induced voltage?

4.A student uses a probe connected to ammeter to detect the magnetic field

close to a coil of wire.

The reading on the meter is zero.

Which of the following will cause the reading on the meter to change?

(1)

  1. Decreasing the number of turns in the coil
  2. Increasing the number of turns in the coil
  3. Passing a current through the coil
  4. Replacing the coil with another coil made of thicker wire
  5. Replacing the coil with another coil made of thinner wire

5.Consider the diagram shown.

a) What happens to the wire when current passes as shown? (1)

b) What would happen to the wire if the direction of the current was reversed? (1)

d) What would happen to the wire if the current and the magnetic field were reversed?

(1)

6. Consider the three diagrams of a model motor shown.

When the current is switched on in A the coil rotates clockwise.

a)What happens to the coil when the current is switched on as shown in B? (1)

b)What happens to the coil when the current is switched on as shown in C? (1)

c)Give three changes that can bemade to the above apparatus to make the coil turn faster. (1)

7.When the bell push is pressed, explain what happens:

i) to the current, (1)

ii) to the soft iron at B, (1)

iii) to the soft iron at C, (1)

iv) to the contact at D, (1)

v) to the current, (1)

vi) to the soft iron B, (1)

vii) to the contact at D. (1)

Total 17 marks