A zener regulator has an input voltage from 15 to 20 V and a load current from 5 to 20 mA. If the zener voltage is 6.8 V, what value should the series resistor have?

In an intrinsic semiconductor, the number of free electrons

A. Equals the number of holes

B. Is less than the number of holes

C. Is greater than the number of holes

D. Impossible to say

E. None of the above

A device that converts mechanical into electrical energy is?

A. solar cell

B. thermocouple

C. chemical cell

D. generator

E. None of the above

Which one of the following kinds of materials has the lowest permeability?

A. A diamagnetic material

B. A paramagnetic material

C. A feiTomagnetic material

D. All of the above

E. None of the above

The total impedance of a parallel RLC circuit:

A. always increases as the applied frequency increases

B. is equal to the sum of the values of resistance, inductive reactance and capacitive reactance

C. always decreases as the applied frequency increases

D. is maximum at the resonant frequency

E. None of the above