What type of current is induced when a magnet moves in and out of a coil?
D.C.
A.C.
U.V.
What is the name of the a.c. generator used in a car?
An indicator
A starter motor
An alternator
A coil of wire is connected to a sensitive centre-zero ammeter. A north pole of a magnet is moved towards the coil before coming to rest inside it. The needle of the ammeter initially deflects to the right. What happens next?
The needle of the ammeter remains deflected to the right
The needle of the ammeter deflects to the left of the centre zero
The needle of the ammeter returns to zero
How can the direction of the current from a generator be reversed?
By changing the direction of the magnetic field
By moving the magnet faster
By changing the direction of the magnetic field, and moving the magnet in the opposite direction
How can the size of the current output from an a.c. generator be increased?
Reverse the direction of rotation
Increase the speed of rotation
Halve the speed of rotation but also reverse the direction of rotation
What is the frequency of mains voltage in the UK?
50 Hz
240 Hz
99.7 MHz
Higher tier only
What is the function of a transformer?
To transfer magnetic fields
To connect separate circuits together
To change the size of the voltage of an alternating current
Which type of current makes a transformer work?
D. C.
U. V.
What kind of transformer converts 230,000 V into 11,500 V?
Step-down transformer
Step-out transformer
Step-up transformer
Why do National Grid overhead transmission cables use very high voltages?
Stepping up voltage means stepping up current, which wastes less energy.
Stepping up voltage means stepping up current, which wastes more energy
Stepping up voltage means stepping down current, which wastes less energy
What type of transformer is used close to domestic consumers to return voltage from the Grid to 230 V, for safe use in the home?