NEET Current Electricity — Set 9

Question 1

A battery of emf $ 15 \, \text{V} $ and internal resistance $ 3 \, \Omega $ is connected to a resistor. If the terminal voltage is $ 12 \, \text{V} $, what is the resistance of the resistor?

Accepted Answer

Voltage drop: $ I r = \varepsilon - V = 15 - 12 = 3 \, \text{V} $. Current: $ I = \frac{3}{r} = \frac{3}{3} = 1 \, \text{A} $. Resistance: $ R = \frac{V}{I} = \frac{12}{1} = 12 \, \Omega $.

Question 2

Why does a conductor exhibit zero net current in the absence of an electric field?

Accepted Answer

Without an electric field, electrons move randomly due to thermal energy, with no preferred direction. The average velocity of electrons cancels out, resulting in zero net current.

Question 3

In a circuit with resistors in parallel, what happens to the voltage across each resistor?

Accepted Answer

In a parallel configuration, all resistors share the same two nodes, so the potential difference (voltage) across each is equal to the source voltage, per Kirchhoff’s loop rule applied to each branch.

NEET Physics: Current Electricity — Practice Set 9

Q1. A battery of emf \( 15 \, \text{V} \) and internal resistance \( 3 \, \Omega \) is connected to a resistor. If the terminal voltage is \( 12 \, \text{V} \), what is the resistance of the resistor?

Q2. Why does a conductor exhibit zero net current in the absence of an electric field?

Q3. In a circuit with resistors in parallel, what happens to the voltage across each resistor?

Q4. A wire of length \( 8 \, \text{m} \) and resistance \( 16 \, \Omega \) is stretched to \( 16 \, \text{m} \). What is the new resistance?

Q5. A \( 6 \, \text{V} \) battery with \( 0.5 \, \Omega \) internal resistance is connected to a \( 5.5 \, \Omega \) resistor. What is the power dissipated in the external resistor?

Q6. A \( 27 \, \text{V} \) battery with negligible internal resistance is connected to a cubical network of 12 resistors, each \( 3 \, \Omega \). What is the total current?

Q7. A wire of length \( 4 \, \text{m} \) and resistance \( 10 \, \Omega \) is stretched to \( 8 \, \text{m} \). What is the new resistance?

Q8. A wire of length \( 4 \, \text{m} \) and cross-sectional area \( 2 \times 10^{-6} \, \text{m}^2 \) has a resistance of \( 8 \, \Omega \). What is the resistivity of the material?

Q9. In a circuit with two cells in series, why does the equivalent internal resistance increase compared to a single cell?

Q10. Two cells in parallel have emf \( 8 \, \text{V} \) and \( 2 \, \text{V} \) with internal resistances \( 2 \, \Omega \) and \( 1 \, \Omega \). What is the equivalent emf?