Question

6.A set of Christmas tree lights consists of 20 identical lamps connected in series
to a 240 V mains supply. What is the potential difference across each lamp?
A. 12 V.
B. 20 V.
C. 240 V.
D. 4807.

Answer 1

GIVEN,

NO. OF LAMPS=20

THOSE LAMPS ARE CONNECTED IN SERIES IT MEANS THE POTENTIAL DIFFERENCE ACROSS EACH BULB IS DIFFERENT AND THE CURRENT FLOWING THROUGH EACH BULB IS SAME.

EMF=240 V

LET THE RESISTANCE OF EACH BULB BE 'R'.THE RESISTANCE OF EACH BULB IS EQUAL AS THEY ARE IDENTICAL WHICH IS GIVEN IN THE QUESTION.

BY OHMS LAW,

V=IR

SUM OF THE VOLTAGES ACROSS EACH RESISTOR=240V

240=I×20R

240/20=IR

IR=12V

WE KNOW THAT POTENTIAL DIFFERENCE(V)=IR

V=12Volts

THEREFORE POTENTIAL DIFFEEENCE ACROSS EACH BULB IS 12Volts.