Voltage, Current and Resistance

1.When the speed at which a conductor is moved through a magnetic field is increased, the induced voltage

increases decreases remains constant reaches zero

2.The induced voltage across a coil with 250 turns that is located in a magnetic field that is changing at a rate of 8 Wb/s is

1,000 V 2,000 V 31.25 V 3,125 V

3.For a given wirewound core, an increase in current through the coil

reverses the flux lines decreases the flux density increases the flux density causes no change in flux density

4.If the cross-sectional area of a magnetic field increases, but the flux remains the same, the flux density

increases decreases remains the same doubles

5.When the current through the coil of an electromagnet reverses, the

direction of the magnetic field reverses direction of the magnetic field remains unchanged magnetic field expands magnetic field collapses

Transformers

1.What kVA rating is required for a transformer that must handle a maximum load current of 8 A with a secondary voltage of 2 kV?

4 kVA 0.25 kVA 16 kVA 8 kVA

2. The turns ratio required to match an 80 source to a 320 ohm load is

80 20 4 2

3.When the turns ratio of a transformer is 20 and the primary ac voltage is 12 V, the secondary voltage is

12V 120V 240V 2400 V

4.If a transformer has 50 turns in the primary winding and 10 turns in the secondary winding, what is the reflective resistance if the secondary load resistance is 250 ?

250 25 6250 62500

5.A certain transformer has 400 turns in the primary winding and 2,000 turns in the secondary winding. The turns ratio is

0.2 0.4 5 25