In a tunnel diode, the negative resistance region occurs due to:

The correct answer is B: Quantum mechanical tunneling through the bandgap. At low forward bias, electrons tunnel through the narrow bandgap, creating peak current. As voltage increases, direct band-to-band current dominates, causing current to decrease with voltage (negative differential resistance).

A Carnot engine operates between temperature reservoirs of 500 K and 300 K. What is its maximum efficiency?

The correct answer is A: 0.40 or 40%. Carnot efficiency: η = 1 - (Tc/Th) = 1 - (300/500) = 1 - 0.60 = 0.40 or 40%

In a fiber optics cable, light undergoes total internal reflection. The minimum refractive index of the core material needed to guide light from air is:

The correct answer is C: 1.414. For total internal reflection at core-cladding boundary: n_core × sin(θc) = n_cladding × 1. For propagation at 45°, n_core ≥ √2 ≈ 1.414

Two slits separated by 0.5 mm are illuminated by light of wavelength 500 nm. The distance to the screen is 1 m. Find the fringe width.

The correct answer is B: 1 mm. Fringe width β = λD/d = (500×10⁻⁹ × 1)/(0.5×10⁻³) = 1×10⁻³ m = 1 mm

An electron enters a region of uniform magnetic field with velocity v perpendicular to the field. If the magnetic field strength is B, the radius of curvature is:

The correct answer is A: r = mv/eB. For a charged particle in a magnetic field, centripetal force equals magnetic force: mv²/r = evB, giving r = mv/eB. This is the radius of the circular path.

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JEE Physics
Current Electricity

Physics questions for JEE Main — Mechanics, Electrostatics, Optics, Modern Physics.

39 Q 9 Topics Take Mock Test

Difficulty: All Easy Medium Hard 11–20 of 39

Topics in JEE Physics

All Mechanics 100 Thermodynamics 100 Electrostatics 100 Current Electricity 100 Magnetism 100 Optics 100 Modern Physics 100 Semiconductors 100 Waves 100

Q.11 Easy Current Electricity

Five resistors each of 5Ω are connected in parallel. The equivalent resistance is:

A 25Ω

B 5Ω

C 1Ω

D 0.2Ω

Correct Answer: C. 1Ω

EXPLANATION

For parallel: 1/R_eq = 5×(1/5) = 1, so R_eq = 1Ω

Test

Q.12 Easy Current Electricity

In a Wheatstone bridge, if P/Q = R/S, then the galvanometer shows zero deflection. This condition is called:

A Balance condition

B Null point

C Both A and B

D Neither A nor B

Correct Answer: C. Both A and B

EXPLANATION

Both balance condition and null point refer to the same situation where no current flows through the galvanometer

Test

Q.13 Easy Current Electricity

Which of the following materials has the lowest temperature coefficient of resistance?

A Copper

B Constantan

C Nichrome

D Aluminum

Correct Answer: B. Constantan

EXPLANATION

Constantan (copper-nickel alloy) has the lowest temperature coefficient of resistance, making it ideal for standard resistors

Test

Q.14 Easy Current Electricity

In a circuit, if the current increases when voltage increases, the resistance must:

A Increase

B Decrease

C Remain constant

D Become zero

Correct Answer: C. Remain constant

EXPLANATION

From Ohm's law: I = V/R. If I increases with increasing V while R stays constant, then the relationship is proportional and follows Ohm's law

Test

Q.15 Easy Current Electricity

In a circuit with a battery of 10V and total resistance 5Ω, the power dissipated is:

A 50W

B 25W

C 20W

D 2W

Correct Answer: C. 20W

EXPLANATION

P = V²/R = (10)²/5 = 100/5 = 20W

Test

Q.16 Easy Current Electricity

In a parallel combination of resistors, the voltage across each resistor is:

A Different for each resistor

B The same for all resistors

C Sum of individual voltages

D Proportional to resistance values

Correct Answer: B. The same for all resistors

EXPLANATION

In parallel combination, all resistors are connected across same two points, hence voltage across each is same

Test

Q.17 Easy Current Electricity

A rheostat is used in a circuit to:

A Measure current

B Vary the current in the circuit

C Measure voltage

D Detect current direction

Correct Answer: B. Vary the current in the circuit

EXPLANATION

A rheostat is a variable resistor used to control and vary the current in a circuit

Test

Q.18 Easy Current Electricity

Three identical cells, each of EMF 1.5V and internal resistance 1Ω, are connected in series. The total EMF and internal resistance are:

A 4.5V, 1Ω

B 1.5V, 3Ω

C 4.5V, 3Ω

D 3V, 3Ω

Correct Answer: C. 4.5V, 3Ω

EXPLANATION

In series: Total EMF = 1.5 + 1.5 + 1.5 = 4.5V. Total internal resistance = 1 + 1 + 1 = 3Ω

Test

Q.19 Easy Current Electricity

A light bulb rated 60W, 120V is connected to a 120V supply. The resistance of the bulb is:

A 120Ω

B 240Ω

C 60Ω

D 180Ω

Correct Answer: B. 240Ω

EXPLANATION

R = V²/P = (120)²/60 = 14400/60 = 240Ω

Test

Q.20 Easy Current Electricity

The resistivity of a material depends on:

A Length of the conductor

B Cross-sectional area of the conductor

C Temperature and nature of the material

D Both length and cross-sectional area

Correct Answer: C. Temperature and nature of the material

EXPLANATION

Resistivity is an intrinsic property depending only on the material type and temperature, not on geometry

Test

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Current Electricity