Current Electricity Important Questions for NEET Physics - 2026

1. Multiple choice questions.

1. The drift velocity of electrons in a conductor increases if:

• (a) Area of cross-section is increased
• (b) Applied potential difference is decreased
• (c) Number density of electrons is decreased
• (d) Length of conductor is decreased

Answer: (c) Number density of electrons is decreased.

2. In a series combination of resistors, the equivalent resistance is:

• (a) Less than the smallest resistor
• (b) Sum of the individual resistances
• (c) Product of the resistances
• (d) Greater than the largest resistor

Answer: (b) Sum of the individual resistances.

3. Which of the following is true for Ohmic conductors?

• (a) Their V-I graph is nonlinear
• (b) Resistance increases with voltage
• (c) V is always proportional to I
• (d) Current does not flow through them

Answer: (c) V is always proportional to I.

4. If the length of a wire is doubled and its area is halved, its resistance becomes:

• (a) 4 times
• (b) 2 times
• (c) Same
• (d) Half

Answer: (a) 4 times.

5. The SI unit of electric conductivity is:

• (a) ohm
• (b) ohm-metre
• (c) mho-metre
• (d) ohm⁻¹-metre⁻¹

Answer: (d) ohm⁻¹-metre⁻¹.

2. Very Short Answer (VSA).

1. What is meant by ‘drift velocity’?

Answer: Drift velocity is the average velocity attained by free electrons in a material when subjected to an electric field.

2. State Ohm’s law.

Answer: Ohm’s law states that the current flowing through a conductor is directly proportional to the potential difference at constant temperature.

3. Define resistivity.

Answer: Resistivity is the property of a material that determines how much it resists electric current, expressed as resistance per unit length per unit area.

4. Write the formula for electrical power in terms of current and resistance.

Answer: The formula is $P = I^2 R$, where $P$ is the power, $I$ is the current, and $R$ is the resistance.

5. What is the function of a Wheatstone bridge?

Answer: A Wheatstone bridge is used to measure an unknown resistance accurately by balancing two legs of a bridge circuit.

3. Short Answer Questions.

1. Explain the relation between mobility and drift velocity of electrons.

Answer: Mobility ($\mu$) is defined as the magnitude of drift velocity acquired per unit electric field. The relation is $v_d = \mu E$, where $v_d$ is drift velocity and $E$ is electric field. Higher mobility means electrons respond quickly to the applied field, resulting in higher current.

2. Distinguish between ohmic and non-ohmic conductors using V-I characteristics.

Answer: Ohmic conductors obey Ohm’s law, showing a straight-line V-I graph, indicating constant resistance. Non-ohmic conductors have nonlinear V-I graphs due to varying resistance with changing voltage or current. Examples include metals (ohmic) and diodes (non-ohmic).

3. A 10m long copper wire has uniform cross-sectional area of $2 \times 10^{-6} m^2$ and a resistance of $0.5\:\Omega$. Find its resistivity.

Answer:

1. Use $R = \rho \dfrac{l}{A}$, where $R = 0.5\:\Omega$, $l = 10$ m, $A = 2 \times 10^{-6}$ m$^2$.
2. $\rho = \dfrac{R A}{l} = \dfrac{0.5 \times 2 \times 10^{-6}}{10} = 1 \times 10^{-7}$ Ωm.

4. Why does resistance of a conductor increase with temperature?

Answer: With rise in temperature, atoms vibrate more vigorously, causing more frequent collisions for free electrons. This increases obstruction to electric current, so resistance increases for most conductors except for materials like semiconductors and insulators.

5. Derive the expression for equivalent resistance when n resistors of resistance R are connected in parallel.

Answer:

1. For parallel: $1/R_{eq} = 1/R + 1/R + ...$ (n terms)
2. $1/R_{eq} = n/R$
3. $\Rightarrow R_{eq} = R/n$

4. True or False Questions.

1. The unit of mobility is m$^2$V$^{-1}$s$^{-1}$.

Answer: True.

2. In an ideal cell, the internal resistance is zero.

Answer: True.

3. The resistance of a metallic conductor decreases with increase in temperature.

Answer: False.

4. Kirchhoff’s junction law is based on the law of conservation of energy.

Answer: False.

5. The potential difference across a resistor is always proportional to the current passing through it.

Answer: True.

3. Fill in the Blanks Questions.

1. The device used to compare an unknown resistance with a standard resistance is called ____________.

Answer: Wheatstone bridge

2. The ratio of the potential difference to current for any conductor is called ____________.

Answer: resistance

3. The resistance of a conductor of length $l$ and cross-sectional area $A$ is given by $R =$ ____________.

Answer: $\rho \dfrac{l}{A}$

4. For a cell, the potential difference across its terminals when no current is drawn equals its ____________.

Answer: emf

5. The unit of electrical power is ____________.

Answer: watt

Strengthening NEET Physics: Importance of Current Electricity Concepts

Building a solid base in Current Electricity is essential for scoring well in NEET Physics. You’ll see questions from topics like Ohm’s law, resistivity, and circuits, so regular practice and clarity of concepts are key to success.

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