Question

A resistance of 10 ohm is connected in series with a combination of two resistance arranged in

parallel, each of 20 ohms. Calculate the value of resistance which should be shunted across the

parallel combination so that the total current drawn by the circuit is 1.5A with applied voltage of

20V.​

Answer 1

Explanation:

The sum of the currents through each path is equal to the total current that flows from the source. You can find total resistance in a Parallel circuit with the following formula: 1/Rt = 1/R1 + 1/R2 + 1/R3 +...

This combination, in turn, is connected to a 10ohm resistor .

As more and more resistors are added in parallel to a circuit, the equivalent resistance of the circuit decreases and the total current of the circuit increases. Adding more resistors in parallel is equivalent to providing more branches through which charge can flow.

What is the effective resistance when two resistance of 10 ohm and 15 ohm are connected in parallel ? Equivalent Resistance = 6 Ohm . This is the required answer .

Let the two resistances be R

1

and R

2

.

Series connection R

s

=R

1

+R

2

Or 80=R

1

+R

2

⟹ R

1

=80−R

2

Parallel connection :

R

p

=

R

1

+R

2

R

1

R

2

Or 20=

80

R

1

(80−R

1

)

Or R

1

2

+80R

1

−1600=0

⟹ R

1

=40Ω

So, R

2

=80−40=40 Ω