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List of Questions

1. Which of the following diagrams best represents the energy bands in p - type and n - type semiconductors?
2. What is an essential requirement for the operation of a step-down transformer?
3. Which of the following would increase the output of a simple DC generator?
4. Blue light is found to cause photoelectric emission from a sodium surface but not from a platinum surface.
   Which of the following best accounts for this difference?
5. An electric motor is connected to a power supply of constant voltage. The motor is allowed to run at different speeds by adjusting a brake. Which graph best shows how the current through the motor varies with speed.
6. The temperature of a metal is refuced. Which statement correctly identifies the change in its electrical resistance and the reason for this change
7. Why does superconductivity occur in certain materials at low temperature?
8. The diagram shows a DC motor with a constant current flowing to the rotor. Which pair of graphs best describes the behaviour of the force F on wire AB, and the torque T on the rotor as fuctions of time t?
9. Which one of the following is a best conductor for electricity
10. A thin solid conductor with sides PQRS is moving at constant velocity v, at right angles to a uniform magnetic field B, directed into the page as shown.