Sunday 24 January 2016

100 PROBLEMS IN ELECTRICAL ENGINEERING - PART – 02 – 05 - PROBLEMS ON POWER DISSIPATION

PROBLEM – 01
A 250 V electric cooking range has three positions of switches high, medium and low. The effective resistance in three positions are 10 ohms, 20 ohms and 40 ohms respectively. There are two identical coils in the ranges. Show how the three position are obtained by proper connection of the coils. Find the power consumed in each position.
PROBLEM – 02
Three resistors Ra, Rb and Rc are connected in series to a 240 V source. If Ra = 2Rc, Rb = 3Rc and total power taken by the circuit is 800 watts. (a) Calculate Ra, Rb and Rc (b) the power consumed by each resistor.
PROBLEM – 03
Four resistors are connected as shown in figure. If the power dissipated in 10 ohm resistor is 50 watts find the value of R and total power supplied by the battery.
PROBLEM – 04
Fiver resistors are connected as shown in figure, values of resistors are in ohms. If power dissipated in 5 ohm resistor is 125 watts. Find the voltage drop across AB, total resistance in the circuit and the current flow through the 15 ohm resistor.
PROBLEM – 05
Figure represents the load resistance Rl = 80 ohms being loaded through a slide wire rheostat. The rheostat has a total resistance of 120 ohms uniformly wound. Calculate the power dissipated to Rl when the slide is in (a) position A, (b) moved down 1/3 from position A (c) moved 2/3 from position A.

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