6. A wire has a resistance of 15 Ω at 20°C and 16.5 Ω at 70°C. What is the temperature coefficient of resistivity?

7. What ensures that the total voltage drop across a series circuit equals the source voltage?

8. A wire of length 2 m and resistance 4 Ω is stretched to 4 m. What is the new resistance?

9. Why does the resistance of a metallic conductor increase with temperature?

10. A nichrome wire has a resistance of 60 Ω at 30°C and α = 1.7 × 10^-4 °C^-1. What is its resistance at 330°C?

11. A Wheatstone bridge has R₁ = 14 Ω, R₂ = 28 Ω, R₃ = 10 Ω. What is R₄ for balance?

12. In a circuit with a battery and a resistor, if the internal resistance of the battery equals the external resistance, what fraction of the total power is dissipated in the external resistor?

13. What causes the resistivity of a conductor to deviate from Ohm's law at very high electric fields?

14. A 16 V battery with 2 Ω internal resistance delivers a current of 2 A to a resistor. What is the resistance of the resistor?

15. What causes the potential difference across a resistor to drop when current flows through it?