The circuit shown has four identical ammeters. A ₂ reads 0.2A and A ₃ reads 0.3A.

1) Findthe current through A1 and A4.

2) Calculate the value of the resistance P.

3) Calculate the potential difference on the voltmeter

4) Calculate the potential difference across the resistance P.

(1)

The current through both ammeters would be same

0.2A + 0.3A = 0.5A as in parallel supply the current gets added.

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(2)

The current through resistor P would be more than 20ohms as less current is flowing through it (0.2A) than the 20 ohms line (0.3A) connected parallel to it. Resistor P allows less amount of current flowing through compared to a 20 ohms resistor, so it is offering more resistance than 20 ohm resistor.

now,

V = IR ; R = V/I

I = 0.2A

V = 6V (shown below)

so,

R = 6/0.2

or R = 30 ohms

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(3)

we know that

V = IR

here I = 0.3A and R = 20 ohms

so,

V = 0.3 x 20 = 6 V

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(4)

The potential difference remains same in parallel connection. So, it will be V = 6V through P.