Electric circuits miscellaneous Easy Questions and Answers | Page - 38

Electric circuits miscellaneous

In the circuit shown below, if the current through the resistor R is zero, what is the value of I?

1. 1 A
1. 2 A
1. 3 A
1. 4A

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When only voltage source

Using KVL in loop (1)
16 – 2 (i₁ + i₂) – 2i₂ = 0
⇒ i₁ + 2i₂ = 8 ...(i)
Using KVL in loop (2)
16 – 2 (i₁ + i₂) – 4i₁ = 0
3i₁ + i₂ = 8 ...(ii)
Solving equations (i) and (ii)
l₂ = 2l₁
Putting in equation (i)
i₁ + 4i₁ = 8
⇒ i₁ = 1.6 Amp
When only current source

i₁' = 2I = 0.4I Amp
2 + 3

Total current through R is zero.
Using superposition theorem
∴ i₁ – i₁' = 0
⇒ 1.6 – 0.4 I = 0
⇒ I = 4 Amp

Correct Option: D

When only voltage source

Using KVL in loop (1)
16 – 2 (i₁ + i₂) – 2i₂ = 0
⇒ i₁ + 2i₂ = 8 ...(i)
Using KVL in loop (2)
16 – 2 (i₁ + i₂) – 4i₁ = 0
3i₁ + i₂ = 8 ...(ii)
Solving equations (i) and (ii)
l₂ = 2l₁
Putting in equation (i)
i₁ + 4i₁ = 8
⇒ i₁ = 1.6 Amp
When only current source

i₁' = 2I = 0.4I Amp
2 + 3

Total current through R is zero.
Using superposition theorem
∴ i₁ – i₁' = 0
⇒ 1.6 – 0.4 I = 0
⇒ I = 4 Amp

Two incandescent light bulbs of 40 W and 60W rating are connected in series across the mains. Then

1. the bulbs together consume 100 W
1. the bulbs together consume 50 W
1. the 60 W bulb glows brighter
1. the 40 bulb glows brighter

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NA

Correct Option: D

NA

The maximum value of mutual inductance of two inductively coupled coils with selfinductance, L₁ = 49 mH and L₂ = 81 mH is

1. 130 mH
1. 63 mH
1. 32 mH
1. 3969 mH

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M < k √L₁ L₂
⇒ M_max = k √L₁ L₂
= √L₁ L₂ = √40 × 81 = 63 mH

Correct Option: B

M < k √L₁ L₂
⇒ M_max = k √L₁ L₂
= √L₁ L₂ = √40 × 81 = 63 mH

From the graphs drawn below, which of the following is non-planer?

1. Fig. (1) and Fig (2)
1. Fig. (2) only
1. Fig (4) only
1. Fig. (3) and Fig. (4)

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This graph is non planar, as it can not be drawn on sheet of paper without using crossing lines .

Correct Option: C

This graph is non planar, as it can not be drawn on sheet of paper without using crossing lines .

If the number of branches in a network is B, the number of nodes is N and the number of dependent loops is L, then the number of independent node equations will be

1. N + L – 1
1. B – 1
1. B – N
1. N – 1

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NA

Correct Option: D

NA