Transformers Number of Coils

A village has to be supplied with electricity from a power station that is a long way from the

village.

Which type of current should be used, and at which voltage?

• Alternating current----------------High voltage

• Alternating current-----------------High voltage

• Direct current------------------High voltage

• Direct current------------------Low voltage

A transformer has Np turns in the primary coil and Ns turns in the secondary coil.

Which row gives the values of Np and Ns for a transformer that steps up a voltage of 1200 V to 36 000 V?

• Np=2,000 Ns=60,000

• Np=2,000 Ns=600,000

• Np=60,000 Ns=2,000

• Np=600,000 Ns=2,000

Why is the core of a transformer made of thin metal strips?

• To reduce eddy currents in the coils which would heat it up and so make the transformer inefficient

• To reduce the weight of the transformer and so make it more efficient

• To increase eddy currents in the coils which would heat it up and so make the transformer inefficient

• None of the above

In a step-up transformer which coil is made of thinner wire?

• The primary coil

• The secondary coil

• Neither,they are the same

A transformer has 1,000 turns on the primary coil and 2,000 turns on the secondary coil. If the input voltage is 12V of d.c, what is the output voltage?

• 24V

• 12V

• 6V

• 0V

A transformer is designed to convert voltage from 240V a.c mains to 12V and has 4,000 turns on its primary coil. How many turns on its secondary coil?

• 100

• 200

• 120

• 480

What is the formula to calculate power loss?

• Voltage drop X Current

• Current X Resistance

• PD X Current X Resistance

• Current² X Resistance