[2](a)A step-down transformer has 2000 turns on its primary coil and 400 turns on its secondary coil. The primary is connected to a 230 V supply. Calculate the secondary voltage.

[2](b)Assuming the transformer is 100% efficient and the primary current is 0.50 A, calculate the secondary current.

[2](a)A wire of length 0.12 m carrying a current of 3.0 A lies at right angles to a magnetic field of flux density 0.25 T. Calculate the force on the wire.

[2](a)State Faraday's Law of electromagnetic induction in words.

[2](b)State two ways of inducing a greater e.m.f. in a coil placed near a moving magnet.

[3](a)Explain how a relay allows a low-current circuit to safely switch on a device that needs a much larger current.

[2](a)A step-up transformer has 500 turns on its primary and 4000 on its secondary, with a 230 V primary supply. Calculate the secondary voltage.

[2](a)A wire of length 0.20 m carries a current of 5 A in a magnetic field of flux density 0.4 T, perpendicular to the wire. Calculate the force on the wire.

[2](a)An ideal transformer has primary voltage 230 V and primary current 2 A, with a secondary voltage of 46 V. Calculate the secondary current, using conservation of power.

[2](a)State two ways to increase the size of the force on a current-carrying wire in a magnetic field.

[1](a)Explain what happens to the induced e.m.f. in a coil if the number of turns on the coil is doubled, with everything else unchanged.

[2](a)Describe, in terms of magnetic flux, what happens as a bar magnet is pushed into a coil connected to a sensitive ammeter.