Q17. A 2-wire distributor is 1500 m Jong and is fed at end A with 250 V d.c. and at end B with 240 V d.c. It supplies four loads: 700 A at 400 m, 600 A at 600 m, 500 A at 1000 m and 300 A at 1200 m, all distances being measured from end A. The resistance of the single conductor is 0.0 l Ω /km.
Calculate EACH of the following:
(a) The current supplied at each end of the distributor;
(b) The voltage across each load;
(c) The total power supplied.
Q7. A non-linear resistor whose characteristic is given by:
l (mA) = 0.1 V2
Is connected in series with a resistor of 680 Ω to a 16 V d.c. supply. Determine EACH of the following:
(a) The value of the voltage across each element;
(b) The circuit current;
(c) The value to which the linear resistance must be changed to give equal voltages across the two elements;
(d) The circuit current for the condition in Q2(c).
Q6. In the two-stage voltage amplifier shown in Fig Q3, both the npn and pnp transistors have high current gains and their leakage currents may be neglected. Transistor T1 has a base-emitter volt drop of 0.7 V and transistor T2 has a base emitter drop of 0.3 V. Calculate EACH of the following:
(a) The voltage between the collector and emitter for each transistor;
(b) The power dissipated in each transistor.
Q2. Two impedances Z1 and Z2 are connected in parallel to a 240 V single phase a.c. supply. The total current drawn is 10 A at unity power factor. Impedance Z1 takes a current of 5A at p.f 0.6 lag.
(a) The current in impedance Z2;
(b) The resistance and reactance of each impedance;
(c) The power dissipated by each impedance.
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.
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