NEET Current Electricity — Set 13

Question 1

A circuit has a $ 14 \, \text{V} $ battery with $ 2 \, \Omega $ internal resistance and two resistors $ 8 \, \Omega $ and $ 4 \, \Omega $ in parallel. What is the total current?

Accepted Answer

Parallel resistance: $ \frac{1}{R_p} = \frac{1}{8} + \frac{1}{4} = \frac{1 + 2}{8} = \frac{3}{8} \Rightarrow R_p = \frac{8}{3} \approx 2.67 \, \Omega $. Total resistance: $ R_{\text{total}} = 2 + 2.67 = 4.67 \, \Omega $. Current: $ I = \frac{\varepsilon}{R_{\text{total}}} = \frac{14}{4.67} \approx 3.0 \, \text{A} $.

Question 2

A circuit has a $ 10 \, \text{V} $ battery with $ 2 \, \Omega $ internal resistance and two resistors $ 4 \, \Omega $ and $ 6 \, \Omega $ in parallel. What is the total current?

Accepted Answer

Parallel resistance: $ \frac{1}{R_p} = \frac{1}{4} + \frac{1}{6} = \frac{3 + 2}{12} = \frac{5}{12} \Rightarrow R_p = \frac{12}{5} = 2.4 \, \Omega $. Total resistance: $ R_{\text{total}} = 2 + 2.4 = 4.4 \, \Omega $. Current: $ I = \frac{\varepsilon}{R_{\text{total}}} = \frac{10}{4.4} \approx 2.27 \, \text{A} $.

Question 3

A $ 10 \, \Omega $ resistor dissipates $ 25 \, \text{W} $ of power. What is the current through it?

Accepted Answer

Power: $ P = I^2 R $. Rearrange: $ I = \sqrt{\frac{P}{R}} $. Substitute: $ I = \sqrt{\frac{25}{10}} = \sqrt{2.5} \approx 1.58 \, \text{A} $.

NEET Physics: Current Electricity — Practice Set 13

Q1. A circuit has a \( 14 \, \text{V} \) battery with \( 2 \, \Omega \) internal resistance and two resistors \( 8 \, \Omega \) and \( 4 \, \Omega \) in parallel. What is the total current?

Q2. A circuit has a \( 10 \, \text{V} \) battery with \( 2 \, \Omega \) internal resistance and two resistors \( 4 \, \Omega \) and \( 6 \, \Omega \) in parallel. What is the total current?

Q3. A \( 10 \, \Omega \) resistor dissipates \( 25 \, \text{W} \) of power. What is the current through it?

Q4. Under what condition does Ohm’s law fail to hold true for a conductor?

Q5. Two cells of emf \( 2 \, \text{V} \) and \( 4 \, \text{V} \) with internal resistances \( 0.5 \, \Omega \) and \( 1.5 \, \Omega \) are connected in series. What is the equivalent emf?

Q6. A wire of length \( 7 \, \text{m} \) and resistance \( 14 \, \Omega \) is stretched to \( 14 \, \text{m} \). What is the new resistance?

Q7. A \( 6 \, \Omega \) resistor dissipates \( 24 \, \text{W} \) of power. What is the current through it?

Q8. A circuit has a \( 10 \, \text{V} \) battery with negligible internal resistance connected to two resistors \( 5 \, \Omega \) and \( 10 \, \Omega \) in series. What is the power dissipated in the \( 10 \, \Omega \) resistor?

Q9. A copper wire of cross-sectional area \( 5 \times 10^{-7} \, \text{m}^2 \) carries a current of \( 1.7 \, \text{A} \). If \( n = 8.5 \times 10^{28} \, \text{m}^{-3} \) and \( e = 1.6 \times 10^{-19} \, \text{C} \), what is the drift speed?

Q10. What is the key factor determining the maximum current a battery can supply?