DieselShip's Online Content Library

Q1. For the circuit shown in fig Q1 determine EACH of the following

(a) The current supplied by each battery:

(b) The voltage across the 8W load resistor:

(c) The power dissipated in the 8W 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.

Q11. A series circuit comprising a 50Ω resistor, a capacitor and a coil having resistance and inductance is connected across a 50 V variable frequency supply.

When the frequency is 400 Hz the current reaches its maximum value of 0.6 A and the voltage across the capacitor is 200 V. Calculate EACH of the following:

(a) The value of the capacitance;

(b) The resistance and inductance of the coil;

(c) The power taken;

(d) The circuit power factor.

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.