Question

Suppose a 6 V battery is connected across a lamp, whose resistance is 20 ohm through a variable resistor as shown in figure.

Answer 1

Answer:

Explanation:

in question given ,

Voltage = 6 volt

current = 0.25 A

resistance = 20ohm

assume R1 be the resistance required from the variable resistances ( a rheostat Rh ) to be placed in series with the lamp.

total resistance in the circuit R = R1 + r = R1 + 20

applying Ohm's law

current = volt / resistance

or,

0.25 = 6 / R1 + 20

R1 + 20 = 6 / 0.25

R1+ 20 = 6×100 / 25 [ replace point)

R1 + 20 = 600/25

R1 + 20 = 24

R 1 = 24 - 20

R1 = 4 ohm

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