Physics Quiz on Electromagnetism

(a) Brush B1 is connected to the positive terminal of the battery and brush B2 is connected to the negative terminal of the battery. (i) On Fig. 8.1, use an arrow to show the direction of the conventional current in the coil. [1] (ii) State the direction in which the coil rotates, when viewed from the end closest to the brushes.

(b) State what difference, if any, each of the following changes makes to the rotation of the coil: (i) using a battery with a larger potential difference, (ii) using a coil with several turns of wire carrying the same current as in (a), (iii) using a stronger magnetic field.

(i) Describe how a voltage across the primary coil causes a voltage across the secondary coil.

(ii) State what design feature would cause the voltage across the secondary coil to be larger than the voltage across the primary coil.

(iii) The output of a power station is connected to a transformer, which you are to assume is 100% efficient. The input to the primary coil is 24 000V, 12 000 A. The output from the secondary coil is 400 000V. This is the voltage at which the electrical energy is transmitted through the transmission lines. Calculate the current in the secondary coil.

(iv) State two reasons why it is cheaper to transmit electrical energy at high voltage. 1. 2.

(i) Explain why the needle deflects as the magnet is inserted.

(ii) State and explain the effect of inserting the magnet more slowly.

(iii) State what is observed when the magnet is withdrawn from the left-hand end of the solenoid.

(a) A solenoid connected to a battery produces a magnetic field. The wires are then connected to the battery terminals the other way round. Tick one box in the table to indicate the effect on the magnetic field.

• decreases but not to zero

• decreases to zero

• reverses direction

• increases

• stays the same