The wire of the potentiometer has resistance 4 ohms and length 1 m. It is connected to a cell of e. m.f. 2 volts and internal resistance 1 ohm. If a cell of e. m.f. 1.2 volts is balanced by it, the balancing length will be:  
A)  90 cm
B)  60 cm
C)  50 cm
D)  75 cm

Potential gradient = 1.6 v/m  

E.M.F. = potential gradient × balancing length 1.2 = 1.6 × l

l=1.2\1.6

=3\4

3\4=0.75m

convert m into cm 0.75x10

0.75m=75 cm

ans=75 cm

Explanation:

a

explanation:

no diagram was provided, but i'm guessing it's the one i've attached to my answer.

here, a mechanical force turns the rod.   this generates an electric current in the coil, which powers the bulb.

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