Current Electricity Study Materials for Competitive Exams

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Current Electricity

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Current Electricity MCQ & Objective Questions

Current Electricity is a crucial topic in physics that students must master for their exams. Understanding this concept not only helps in grasping fundamental principles but also significantly boosts your performance in objective questions. Practicing MCQs and important questions related to Current Electricity can enhance your exam preparation and increase your chances of scoring higher marks.

What You Will Practise Here

Ohm's Law and its applications
Series and parallel circuits
Electrical power and energy calculations
Resistance, resistivity, and factors affecting resistance
Kirchhoff's laws and their practical applications
Concept of current, voltage, and their relationship
Diagrams and circuit analysis techniques

Exam Relevance

The topic of Current Electricity is frequently tested in various examinations, including CBSE, State Boards, NEET, and JEE. Students can expect questions that assess their understanding of fundamental concepts, application of formulas, and problem-solving skills. Common question patterns include numerical problems, theoretical questions, and circuit analysis, making it essential to be well-prepared with Current Electricity MCQ questions.

Common Mistakes Students Make

Confusing current with voltage and their units
Misapplying Ohm's Law in complex circuits
Overlooking the effects of temperature on resistance
Failing to differentiate between series and parallel connections
Neglecting to draw circuit diagrams for better understanding

FAQs

Question: What is the formula for calculating electrical power?
Answer: The formula for electrical power is P = VI, where P is power, V is voltage, and I is current.

Question: How does resistance change in series and parallel circuits?
Answer: In series circuits, total resistance increases, while in parallel circuits, total resistance decreases.

Now is the time to enhance your understanding of Current Electricity! Dive into our practice MCQs and test your knowledge to ensure you are well-prepared for your exams. Start solving today and boost your confidence!

Circuits & Kirchhoff Laws Ohms Law Potentiometer Resistivity Wheatstone Bridge

Q. A 10-ohm resistor has a voltage of 20 volts across it. What is the current flowing through the resistor?

A. 1 A
B. 2 A
C. 3 A
D. 4 A

Solution

Using Ohm's Law, I = V / R = 20 V / 10 Ω = 2 A.

Correct Answer: B — 2 A

Q. A 10-ohm resistor has a voltage of 50 volts across it. What is the current flowing through the resistor?

A. 5 A
B. 10 A
C. 15 A
D. 20 A

Solution

Using Ohm's Law, I = V / R = 50 V / 10 Ω = 5 A.

Correct Answer: B — 10 A

Q. A 10-ohm resistor is connected to a 20-volt battery. What is the power dissipated by the resistor?

A. 40 W
B. 20 W
C. 10 W
D. 2 W

Solution

Power (P) can be calculated using P = V^2 / R = 20^2 / 10 = 400 / 10 = 40 W.

Correct Answer: A — 40 W

Q. A 5 ohm resistor and a 10 ohm resistor are connected in series. What is the total resistance?

A. 15 ohms
B. 5 ohms
C. 10 ohms
D. 2 ohms

Solution

In series, the total resistance is R_total = R1 + R2 = 5 + 10 = 15 ohms.

Correct Answer: A — 15 ohms

Q. A 60W bulb is connected to a 120V supply. What is the resistance of the bulb?

A. 240 ohms
B. 120 ohms
C. 60 ohms
D. 30 ohms

Solution

Using P = V^2 / R, we rearrange to find R = V^2 / P = (120V)^2 / 60W = 240 ohms.

Correct Answer: B — 120 ohms

Q. A circuit contains a 10Ω resistor and a 5Ω resistor in series with a 15V battery. What is the total current in the circuit?

A. 1A
B. 2A
C. 3A
D. 4A

Solution

Total resistance R = 10Ω + 5Ω = 15Ω. Current I = V/R = 15V/15Ω = 1A.

Correct Answer: B — 2A

Q. A circuit contains a 10Ω resistor and a 5Ω resistor in series. What is the total resistance?

A. 5Ω
B. 10Ω
C. 15Ω
D. 50Ω

Solution

In series, total resistance R = R1 + R2 = 10Ω + 5Ω = 15Ω.

Correct Answer: C — 15Ω

Q. A circuit contains a 12 V battery and two resistors of 4 ohms and 8 ohms in series. What is the current flowing through the circuit?

A. 0.5 A
B. 1 A
C. 1.5 A
D. 2 A

Solution

Total resistance R = 4 + 8 = 12 ohms. Current I = V/R = 12 V / 12 ohms = 1 A.

Correct Answer: B — 1 A

Q. A circuit contains a 12V battery and two resistors of 4 ohms and 8 ohms in series. What is the total current in the circuit?

A. 1 A
B. 0.5 A
C. 2 A
D. 3 A

Solution

Total resistance R = R1 + R2 = 4 + 8 = 12 ohms. Current I = V/R = 12V / 12 ohms = 1 A.

Correct Answer: B — 0.5 A

Q. A circuit contains a 9V battery and two resistors in series: 3Ω and 6Ω. What is the voltage across the 6Ω resistor?

A. 6V
B. 3V
C. 9V
D. 0V

Solution

The total resistance R_total = 3Ω + 6Ω = 9Ω. The current I = V/R_total = 9V / 9Ω = 1A. Voltage across 6Ω, V = I * R = 1A * 6Ω = 6V.

Correct Answer: A — 6V

Q. A circuit contains a 9V battery and two resistors of 3 ohms and 6 ohms in series. What is the voltage across the 6 ohm resistor?

A. 6V
B. 3V
C. 9V
D. 4.5V

Solution

Total resistance R_total = 3 + 6 = 9 ohms. Current I = V/R_total = 9V / 9Ω = 1 A. Voltage across 6 ohm resistor = I * R = 1 A * 6Ω = 6V.

Correct Answer: A — 6V

Q. A circuit contains a 9V battery and two resistors of 3 ohms and 6 ohms in series. What is the voltage drop across the 6 ohm resistor?

A. 3 V
B. 6 V
C. 9 V
D. 4.5 V

Solution

Total resistance R_total = 3 + 6 = 9 ohms. Current I = V/R_total = 9V / 9Ω = 1 A. Voltage drop across 6 ohm resistor = I * R = 1 A * 6Ω = 6 V.

Correct Answer: B — 6 V

Q. A circuit contains a 9V battery and two resistors of 3Ω and 6Ω in series. What is the voltage across the 6Ω resistor?

A. 6V
B. 3V
C. 9V
D. 0V

Solution

The total resistance R_total = 3Ω + 6Ω = 9Ω. The current I = V/R_total = 9V / 9Ω = 1A. Voltage across 6Ω, V = I * R = 1A * 6Ω = 6V.

Correct Answer: A — 6V

Q. A circuit has a total resistance of 10 ohms and a current of 5 A. What is the total voltage in the circuit?

A. 50 V
B. 10 V
C. 5 V
D. 2 V

Solution

Using Ohm's law, V = I * R = 5 A * 10 ohms = 50 V.

Correct Answer: A — 50 V

Q. A circuit has a voltage of 12 volts and a resistance of 4 ohms. What is the current flowing through the circuit?

A. 3 A
B. 4 A
C. 2 A
D. 1 A

Solution

Using Ohm's Law, I = V / R = 12 V / 4 Ω = 3 A.

Correct Answer: A — 3 A

Q. A circuit has a voltage of 12V and a resistance of 4Ω. What is the current flowing through the circuit?

A. 3A
B. 4A
C. 12A
D. 48A

Solution

Using Ohm's Law, I = V/R = 12V / 4Ω = 3A.

Correct Answer: A — 3A

Q. A circuit has a voltage of 24 volts and a current of 6 amperes. What is the resistance?

A. 4 Ω
B. 6 Ω
C. 8 Ω
D. 12 Ω

Solution

Using Ohm's Law, R = V / I = 24 V / 6 A = 4 Ω.

Correct Answer: A — 4 Ω

Q. A copper wire has a resistivity of 1.68 x 10^-8 Ω·m. What is the resistance of a 100 m long wire with a cross-sectional area of 1 mm²?

A. 1.68 Ω
B. 0.168 Ω
C. 0.0168 Ω
D. 16.8 Ω

Solution

Resistance (R) = ρ * (L / A) = 1.68 x 10^-8 * (100 / 1 x 10^-6) = 1.68 Ω.

Correct Answer: A — 1.68 Ω

Q. A cylindrical conductor has a length L and radius r. If the radius is doubled while keeping the length constant, how does the resistivity change?

A. Doubles
B. Halves
C. Remains the same
D. Increases four times

Solution

Resistivity is an intrinsic property of the material and does not change with geometry.

Correct Answer: C — Remains the same

Q. A cylindrical conductor has a length of 1 m and a radius of 0.01 m. If its resistivity is 2 x 10^-8 Ω·m, what is its resistance?

A. 0.01 Ω
B. 0.02 Ω
C. 0.03 Ω
D. 0.04 Ω

Solution

Resistance R = ρ * (L / A) = 2 x 10^-8 * (1 / (π * (0.01)²)) = 0.02 Ω.

Correct Answer: B — 0.02 Ω

Q. A cylindrical wire has a length of 1 m and a radius of 0.5 mm. If its resistivity is 1.68 x 10^-8 Ω·m, what is its resistance?

A. 0.0212 Ω
B. 0.0424 Ω
C. 0.0848 Ω
D. 0.168 Ω

Solution

Resistance R = ρ(L/A) = 1.68 x 10^-8 * (1 / (π(0.5 x 10^-3)²)) = 0.0424 Ω.

Correct Answer: B — 0.0424 Ω

Q. A potentiometer is used to compare two emf sources. If the first source gives a balance length of 60cm and the second gives 90cm, what is the ratio of their emfs?

A. 2:3
B. 3:2
C. 1:1
D. 4:5

Solution

The ratio of emfs is equal to the ratio of the balance lengths, so it is 60cm:90cm = 2:3.

Correct Answer: B — 3:2

Q. A potentiometer is used to compare two EMFs. If the known EMF is 6V and the length of the wire is 120 cm, what is the potential gradient if the length of the wire is used to balance an unknown EMF of 4V?

A. 0.05 V/cm
B. 0.03 V/cm
C. 0.04 V/cm
D. 0.02 V/cm

Solution

The potential gradient is calculated as (6V / 120 cm) = 0.05 V/cm. For the unknown EMF of 4V, the length used would be (4V / 0.05 V/cm) = 80 cm.

Correct Answer: C — 0.04 V/cm

Q. A potentiometer wire has a length of 10 m and a potential difference of 5 V across it. What is the potential gradient?

A. 0.5 V/m
B. 1 V/m
C. 2 V/m
D. 5 V/m

Solution

The potential gradient is calculated as the potential difference divided by the length of the wire: 5 V / 10 m = 0.5 V/m.

Correct Answer: A — 0.5 V/m

Q. A potentiometer wire has a resistance of 10 ohms and is connected to a 5 V battery. What is the current flowing through the wire?

A. 0.5 A
B. 1 A
C. 2 A
D. 5 A

Solution

Using Ohm's law (V = IR), the current can be calculated as I = V/R = 5 V / 10 ohms = 0.5 A.

Correct Answer: B — 1 A

Q. A potentiometer wire has a uniform cross-section and a length of 10 m. If a potential difference of 5 V is applied, what is the potential gradient?

A. 0.5 V/m
B. 1 V/m
C. 2 V/m
D. 5 V/m

Solution

The potential gradient is calculated as V/L = 5 V / 10 m = 0.5 V/m.

Correct Answer: B — 1 V/m

Q. A potentiometer wire has a uniform cross-section and a potential difference of 12V across it. If the length of the wire is 6m, what is the potential gradient?

A. 2 V/m
B. 4 V/m
C. 6 V/m
D. 8 V/m

Solution

Potential gradient = Voltage / Length = 12V / 6m = 2 V/m.

Correct Answer: B — 4 V/m

Q. A potentiometer wire has a uniform cross-section and a total length of 10 m. If a potential difference of 5 V is applied across it, what is the potential gradient?

A. 0.5 V/m
B. 1 V/m
C. 2 V/m
D. 5 V/m

Solution

The potential gradient is calculated as V/L = 5 V / 10 m = 0.5 V/m.

Correct Answer: B — 1 V/m

Q. A potentiometer wire is made of constantan. What is the advantage of using this material?

A. High conductivity
B. Low temperature coefficient
C. High resistance
D. Low cost

Solution

Constantan has a low temperature coefficient, making it stable for accurate measurements.

Correct Answer: B — Low temperature coefficient

Q. A resistor of 10 ohms is connected to a 20V battery. What is the current flowing through the resistor?

A. 0.5 A
B. 1 A
C. 2 A
D. 5 A

Solution

Using Ohm's Law, I = V/R = 20V / 10Ω = 2 A.

Correct Answer: C — 2 A

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