76
Question
Suppose a 6V battery is connected across a lamp , whose resistance is 20ohm , through the variable resistor . if the current in the circuit is 0.25A , calculate the value of the resistance from the resistor which must be used ?
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Solution
Given,
Battery voltage, V=6 V
Current in circuit, I=0.25 A
Lamp resistance, R=20 ohm
Extra resistance, R'=?
For the series combination of R and R',
R''=R+R'
Using Ohm's law,
R''=V/I
=6/0.25=24 ohm
But, R''=R+R'
Or R'=R''-R=24-20=4 ohm
Battery voltage, V=6 V
Current in circuit, I=0.25 A
Lamp resistance, R=20 ohm
Extra resistance, R'=?
For the series combination of R and R',
R''=R+R'
Using Ohm's law,
R''=V/I
=6/0.25=24 ohm
But, R''=R+R'
Or R'=R''-R=24-20=4 ohm
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