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Q24. (a) For the circuit shown in Fig Q1, calculate EACH of the following;

(i) The current through the 12 Ω resistor;

(ii) The p.d. across each resistor.

(b) Calculate the voltage VAB if the 12 Ω resistor is now removed from the circuit.

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.

Q16. The p.d. between base and emitter for the transistor shown in Fig Q4 is 0.4 V and the steady state output voltage is 6 V. The base current is negligible. Calculate EACH of the following:

(a) The p.d. between the base and earth;

(b) The collector current;

(c) The value of the load resistor RL;

(d) The power dissipated in the 180 Ω resistor;

(e) The power dissipated in the transistor.

Q18. A star connected unbalanced three phase load is connected to a four-wire supply with a phase voltage of 240 V a.c. The resistive loads in each of the three phases are as follows:

Red to neutral 40 Ω; yellow to neutral 50 Ω; blue to neutral 60 Ω. Determine EACH of the following:

(a) The current in each phase;

(b) The current in the neutral wire;

(c) The phase angle between the neutral current and the voltage VRN.

Q6. A 3ph 440 V 60 Hz 8 pole induction motor runs at a power factor of 0.85 lag and drives a load of 8 kW at a speed of 14.4 rev/sec. The stator loss is 1 kW and the rotational losses (windage and friction) amount to 0.8 kW. Calculate EACH of the following:

(a) The synchronous speed;

(b) The rotor copper loss;

(c) The input power to the motor;

(d) The motor current.