Question Details

Three resistors having resistances r1, r2 and r3 are connected as shown in the given circuit. The ratio i₃/i₁ of currents in terms of resistances used in the circuit is :

Options

A

r₁/r₂+r₃

B

r₂/r₂+r₃

C

r₁/r₁+r₂

D

r₂/r₁+r₃

Correct Answer :

r₂/(r₂ + r₃)

Solution :

The correct option is r₂/(r₂ + r₃).

Step-by-step Explanation:

1. Identify the current division:
From the given circuit diagram, we can see that the total current entering terminal A is i1, which passes through resistor r1. At the junction, this current splits into two parallel branches containing resistors r2 and r3 carrying currents i2 and i3 respectively. According to Kirchhoff's Current Law (KCL):

i1=i2+i3

2. Apply the parallel voltage relation:
Since the resistors r2 and r3 are connected in parallel, the potential difference (voltage drop) across both resistors is equal. By Ohm's law:

i2r2=i3r3

3. Express i2 in terms of i3:

i2=i3r3r2

4. Substitute i2 back into the current equation:

i1=i3r3r2+i3

Factoring out i3 gives:

i1=i3r3r2+1

Simplifying the expression in the parentheses:

i1=i3r2+r3r2

5. Find the ratio i3i1:
Rearranging the equation to solve for the ratio of i3 to i1:

i3i1=r2r2+r3

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