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Q3. A power silicon transistor with the characteristics given in Worksheet Q3 is operated from

a 16V d.c. supply. The operating (quatient’s) point is  = 40 mA and  = 2 mA.

Determine EACH of the following:

(a) Draw the load line on the characteristics;

(b) (i) The value of the collector load resistance;

(ii) The peak to peak variation in collector if a signal of  20 mA is applied to the base;

(iii) The corresponding variation in collector current',

(iv) The power dissipated in the transistor due to this signal

Q8. An a.c. series circuit consists of four elements as shown in Fig Q4. The power dissipated in the 50Ω resistor is 200 W and the volt drops across the various parts of the circuit are as shown.

Calculate EACH of the following:

(a) The values of C and L;

(b) The overall power factor of the circuit;

(c) The kVAR for the inductance.

Q7. A 440 V/110 V single phase transformer takes a no-load current of 5 A at power factor 0.25 lag. On load the transformer supplies 7.5 kV A at power factor 0.8 lag.

Calculate EACH of the following, for the on-load condition:

(a) The transformer secondary current;

(b) The transformer primary current;

(c) The primary power factor;

(d) The efficiency of the transformer at this load.