Electric circuits miscellaneous
- In the figure below, the current of 1 ampere flows through the resistance of _________ ohms
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There are three parallel banks which are in turn connected in series Equivalent resistance of 20 ohm and 30 ohm parallel resistors
= 20 × 30 = 12 ohms . 10 + 15
Equivalent resistance of 6 ohm, 4 ohm and 12 ohm bank = 2 ohms.
Total resistance of the circuit = 12 + 2 + 6 = 20 ohms
∴ Current drawn from supply = V = 120 = 6 A I 20 Current through 20 ohms resistor = 6 × 30 = 3.6 A 20 + 30
Current through 30 ohms resistor = 6 – 3.6 = 2.4
A Equivalent resistance of 6 ohm, 4 ohm and 12 ohm bank = 2 ohm,
Voltage drop = 6 × 2 = 12 V.∴ Current through 6 ohm resistor = 12 = 2 A 6 Current through 4 ohm resistor = 12 = 3 A 4 Current through 12 ohm resistor = 12 = 1A 12 Correct Option: A
There are three parallel banks which are in turn connected in series Equivalent resistance of 20 ohm and 30 ohm parallel resistors
= 20 × 30 = 12 ohms . 10 + 15
Equivalent resistance of 6 ohm, 4 ohm and 12 ohm bank = 2 ohms.
Total resistance of the circuit = 12 + 2 + 6 = 20 ohms
∴ Current drawn from supply = V = 120 = 6 A I 20 Current through 20 ohms resistor = 6 × 30 = 3.6 A 20 + 30
Current through 30 ohms resistor = 6 – 3.6 = 2.4
A Equivalent resistance of 6 ohm, 4 ohm and 12 ohm bank = 2 ohm,
Voltage drop = 6 × 2 = 12 V.∴ Current through 6 ohm resistor = 12 = 2 A 6 Current through 4 ohm resistor = 12 = 3 A 4 Current through 12 ohm resistor = 12 = 1A 12
- The current waveform in a pure resistor at 10 Ω is shown in the given figure. power dissipated in the resistor is ______ W
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Power = I2R = 27 × 10 = 270 WCorrect Option: D
Power = I2R = 27 × 10 = 270 W
- At a certain current, the energy stored in iron cored coil is 1000 J and its copper loss is 2000 W. The time constant (in seconds) of the coil is_____
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Time constant, T = L = I2 L = 2 × 1000 = 1 R I2 R 2000 Correct Option: B
Time constant, T = L = I2 L = 2 × 1000 = 1 R I2 R 2000
- The energy stored in the magnetic field at a solenoid 30 cm long and 3 cm diameter wound with 1000 turns of wire carrying a current at 10 A, is ________ Joules
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L = N2μ0A = 106 × 4π × 10-7 × (π / 4) × (9 × 10-4) l 0.3 = 9π2 × 10-5 0.3 ∴ Energy = 1 LI2 = 0.148 or 0.15 Joules 2
Correct Option: A
L = N2μ0A = 106 × 4π × 10-7 × (π / 4) × (9 × 10-4) l 0.3 = 9π2 × 10-5 0.3 ∴ Energy = 1 LI2 = 0.148 or 0.15 Joules 2
- A 35 V source is connected to a series circuit at 600 ohms and R as shown. If a voltmeter at internal resistance 1.2 kilo ohms is connected across 600 ohm resistor it reads 5 V. The value of R is ______k Ω .
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When voltmeter of 1.2 kΩ meter resistance is connected across 600 Ω , then
net resistance becomes 600 × 1200 = 400 Ω 600 × 1200 
Voltage across this is 5 V and therefore voltage across R is 35 – 5 = 30 V
∴ R = VR = 30 400 V 5
⇒ R = 2.4 kΩCorrect Option: C
When voltmeter of 1.2 kΩ meter resistance is connected across 600 Ω , then
net resistance becomes 600 × 1200 = 400 Ω 600 × 1200
Voltage across this is 5 V and therefore voltage across R is 35 – 5 = 30 V
∴ R = VR = 30 400 V 5
⇒ R = 2.4 kΩ
