NEET Current Electricity — Set 4

Question 1

Why does a non-ohmic device, like a diode, exhibit a non-linear current-voltage relationship?

Accepted Answer

In a diode, resistance depends on the direction and magnitude of the applied voltage due to its semiconductor junction properties. Forward bias reduces resistance, while reverse bias increases it, leading to a non-linear $ I $-versus-$ V $ curve.

Question 2

A Wheatstone bridge with $ R_1 = 10 \, \Omega $, $ R_2 = 20 \, \Omega $, $ R_3 = 15 \, \Omega $, $ R_4 = 30 \, \Omega $ has a $ 15 \, \text{V} $ battery across AC and a galvanometer ($ 10 \, \Omega $) across BD. What is the current through the galvanometer?

Accepted Answer

Check balance: $ \frac{R_1}{R_2} = \frac{10}{20} = 0.5 $, $ \frac{R_3}{R_4} = \frac{15}{30} = 0.5 $. Bridge is balanced. Since balanced, $ I_g = 0 \, \text{A} $.

Question 3

A $ 12 \, \Omega $ resistor dissipates $ 48 \, \text{W} $ of power. What is the voltage across it?

Accepted Answer

Power: $ P = \frac{V^2}{R} $. Rearrange: $ V = \sqrt{P R} $. Substitute: $ V = \sqrt{48 \times 12} = \sqrt{576} = 24 \, \text{V} $.

NEET Physics: Current Electricity — Practice Set 4

Q1. Why does a non-ohmic device, like a diode, exhibit a non-linear current-voltage relationship?

Q2. A Wheatstone bridge with \( R_1 = 10 \, \Omega \), \( R_2 = 20 \, \Omega \), \( R_3 = 15 \, \Omega \), \( R_4 = 30 \, \Omega \) has a \( 15 \, \text{V} \) battery across AC and a galvanometer (\( 10 \, \Omega \)) across BD. What is the current through the galvanometer?

Q3. A \( 12 \, \Omega \) resistor dissipates \( 48 \, \text{W} \) of power. What is the voltage across it?

Q4. A wire has a resistance of \( 12 \, \Omega \) at \( 25^\circ \text{C} \) and \( 13.2 \, \Omega \) at \( 85^\circ \text{C} \). What is the temperature coefficient of resistivity?

Q5. Why does the drift velocity of electrons in a conductor remain much smaller than their thermal velocity?

Q6. A Wheatstone bridge with \( R_1 = 4 \, \Omega \), \( R_2 = 8 \, \Omega \), \( R_3 = 6 \, \Omega \), \( R_4 = 12 \, \Omega \) has a \( 12 \, \text{V} \) battery across AC and a galvanometer (\( 2 \, \Omega \)) across BD. What is the current through the galvanometer?

Q7. A Wheatstone bridge with \( R_1 = 16 \, \Omega \), \( R_2 = 32 \, \Omega \), \( R_3 = 24 \, \Omega \), \( R_4 = 48 \, \Omega \) has a \( 20 \, \text{V} \) battery across AC and a galvanometer (\( 5 \, \Omega \)) across BD. What is the current through the galvanometer?

Q8. A circuit has a \( 12 \, \text{V} \) battery with \( 1 \, \Omega \) internal resistance and two resistors \( 2 \, \Omega \) and \( 6 \, \Omega \) in parallel. What is the total current?

Q9. A \( 18 \, \text{V} \) battery with negligible internal resistance is connected to a cubical network of 12 resistors, each \( 3 \, \Omega \). What is the total current?

Q10. A cell of emf \( 5 \, \text{V} \) and internal resistance \( 0.5 \, \Omega \) is connected to a \( 4.5 \, \Omega \) resistor. What is the current in the circuit?