Aptitude Test Problems in Physics Science for Everyone by S Krotov ( PDFDrive.com )

3. Electricity and Magnetism 97

3.57. A winch is driven by an electric mo-

tor with a separate excitation and fed from

a battery of emf 6 = 300 V. The rope and

the hook of the winch rise at a velocity

vl = 4 m/s without a load and at a velocity

v 2 = 1. m/s with a load of mass m = 10 kg.

Cathode

—127V

Fig. 110 Fig. 111

Determine the velocity v' of the load and

its mass m' for which the winch has the

maximum power, neglecting the mass of the

rope and the hook.

3.58. A perfect diode is connected to an a.c.

circuit (Fig. 111).

Determine the limits within which the

voltage between the anode and the cathode

varies.

3.59. A capacitor of unknown capacitance,

a coil of inductance L, and a resistor of re-

R

Fig. 112

sistance R are connected to a source of a.c.

voltage e Wo cos wt (Fig. 112). The cur-

rent in the circuit is I = (e (^0) 1R) cos wt.
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