Gr 9_Asg Generator & Transformer

A step-down transformer is 100% efficient. It has an input voltage of 240 V a.c. and an output voltage of 60 V a.c.

The current in the primary coil is 0.50 A.

What is the current in the secondary coil?

• 0.13 A

• 0.50 A

• 2.0 A

• 8.0 A

The diagram shows a transformer. What is the output voltage?

• 0.35 V

• 2.9 V

• 4600 V

• 105 000 V

In an a.c. generator, a coil is rotated in a magnetic field and an electromotive force (e.m.f.) is induced in the coil. In which position of the coil does the e.m.f. have the largest value?

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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 = 2000

  Ns = 60 000

• Np = 2000

  Ns = 600 000

• Np = 60 000

  Ns = 2000

• Np = 600 000

  Ns = 2000

The diagram shows a transformer.

The input voltage is 240 V. What is the output voltage?

• 6.0 V

• 12 V

• 20 V

• 40 V

Transformers are used in the transmission of electrical power to houses. Which type of transformer is used at the power station prior to connection to the power lines and which type is used prior to delivery to the houses?

• Power station: Step Down

  Before Houses: Step Down

• Power station: Step Down

  Before Houses: Step Up

• Power station: Step Up

  Before Houses: Step Down

• Power station: Step Up

  Before Houses: Step Up

The diagram shows an a.c. generator rotating in a clockwise direction.

What are the names of parts 1 and 2?

• 1: Brush

  2: Slip Ring

• 1: Brush

  2: Slip Ring Commutator

• 1: Slip Ring

  2: Slip Brush

• 1: Slip Ring

  2: Slip Ring Commutator

The diagram shows a wire between two magnets. An electromotive force (e.m.f.) is induced in the wire when it is moved up between the two magnets.

Four tests are done.

1 The direction of movement of the wire is reversed.

2 The direction of the magnetic field is reversed.

3 The wire is moved more quickly.

4 The magnetic field strength is decreased.

Which tests will induce a smaller e.m.f. in the wire?

• 1 and 2

• 1 and 3

• 3 and 4

• 4 only

The diagram shows an a.c. generator used to power a lamp. The coil rotates in a clockwise direction.

Which magnetic poles are X and Y?

• X: N Pole

  Y: N Pole

• X: N Pole

  Y: S Pole

• X: S Pole

  Y: N Pole

• X: S Pole

  Y: S Pole

A transformer is needed to convert a supply of 240 V a.c. into 4800 V a.c.

Which pair of coils would be suitable for this transformer?

• number of turns

  on primary coil NP= 50

  number of turns

  on secondary coil NS= 1000

• number of turns

  on primary coil NP= 240

  number of turns

  on secondary coil NS= 48 000

• number of turns

  on primary coil NP= 480

  number of turns

  on secondary coil NS= 24

• number of turns

  on primary coil NP= 2000

  number of turns

  on secondary coil NS= 100