Page 33 - CHAPTER-1 (Electricity)

CHAPTER 1

ELECTRICITY

is the reason for connecting electrical appliances in parallel

combination in the household circuit.

Mental floss!

If a wire of resistance R, cut in n equal parts and then the parts are

collected to form a bundle, then, the equivalent resistance of

R
combination will be .
n 2

Example 11:

Two 40Ω resistors and a 20Ω resistor are all connected in parallel with

a 12V power supply. Compute their effective resistance as well as the

current through each resistor. What is the current flowing through the

supply?

Solution:

According to the circuit, the three resistors are connected in parallel

combination, the effective resistance,

1 1 1 1 1 1 1
=
+
+
R R 1 + R 2 + R 3 = 40 40 20 ⟹R=10Ω
So, the three resistors together have an effective resistance of 10Ω.

Each resistor has a potential difference of 12V across it. Because in

parallel combination, the potential difference across each resistance is

equal to the total potential difference applied to the combination.

We know that,

Current (I) = Potential difference (V)
Resistance (R)

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