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Q6. In the network shown in Fig Q1, the meter indicates 2 mA in the direction shown.

Determine EACH of the following:

(a) The resistance of the meter;

(b) The reading on the meter if the 1.5 kΩ and the 2 kΩ resistors are interchanged.

Q1. The V/I characteristic of a non-linear resistor is shown in Table Q2.

This non-linear resistor is connected in series with a paralleled pair of resistors of 40 kW and 60 kW and the overall circuit is supplied at 120 V d.c. Determine graphically or otherwise:

(a) The current in the non-linear resistor;

(b) The effective resistance of the non-linear resistor;

(c) The current in the 40 kW resistor.

Q1. A small silicon transistor with the characteristics given in Worksheet Q3 has a maximum safe power dissipation of 18 mW and it is to be operated on a 12 volt d.c. supply.

(a) Plot the maximum power dissipation curve on the characteristics.

(b) Determine the minimum value of collector load resistance for the transistor if this dissipation is not to be exceeded.

(c) If the transistor is used in a common emitter configuration and is biased at a base current of 60 mA and an alternating signal of  40 mA is applied to the base,

determine EACH of the following:

(i) The r.m.s. voltage variation between collector and emitter;

(ii) The r.m.s. value of the variation in collector current.

Q1. (a) A coil having resistance and inductance is connected to a 240 V, 50 Hz supply and draws a current of 4A at power factor 0.8 lag. Determine EACH of the following:

(i) The resistance of the coil;

(ii) The inductance of the coil.

(b) A capacitor is now joined in series with the coil and the current rises to 5A.

Determine EACH of the following:

(i) The value of the capacitor;

(ii) The new power factor.

Q3. 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 kVA at power factor 0.8 lag. Calculate EACH of the following:

(a) The transformer secondary current;

(b) The transformer primary current;

(c) The primary power factor;

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