Very Short Answer Questions - 1 Mark
Que 1. The voltage-current (v-I) graph of a metallic conductor at two different temperature T1 and T2 is shown in figure. At which temperature is the resistance higher?
Ans. At T2.
Que 2. Why is resistance less when resistors are joined in parallel?
Ans. We know that 
In parallel combination of resistors, the effective area of cross-section of the conductor increases, to the resistance decreases.
Que 3. Why is resistance more in series combination?
Ans. We know R ∞ L. In series combination of resistors, the effective length of cross-section of the conductor increases, so the resistance increases.
Que 4. What are the special features of a heating wire?
Ans. It must have high specific resistance and high melting point.
Que 5. What is the resistance of an ideal ammeter?
Ans. Zero.
Que 6. What is the resistance of an ideal voltmeter?
Ans. Infinite
Que 7. Which one has more resistance 100 watt bulb or 60 watt bulb both operating at 220 V?
Ans. The resistance of 60 watt bulb is greater than the resistance of 100 watt bulb.
Que 8. Write the expression for the heat energy produced in a wire of resistance R and carrying current I.
Ans. Heat produced, H = I2 Rt, where‘t’ stands for time, for which current l is passed through the conductor.
Que 9. Name the physical quantity whose unit is J/C.
Ans. Electric potential.
Que 10. What is the resistance of an air gap?
Ans. It is very large, almost infinite.
Que 11. What is the commercial unit of electric energy?
Ans. The commercial unit of electric energy is kilowatt hour (kWh).
Que 12. What happens to the resistance of a wire if it is made thinner?
Ans. The resistance of wire increases.
Que 13. In series combination which remains constant-current or voltage?
Ans. Current.
Que 14. Which substance is used for making resistance coil of electric heater and why?
Ans. Nichrome, due to its high resistivity.
Que 15. Which physical quantity remains constant when resistances are connected in parallel?
Ans. Potential difference (voltage) remains constant.
Que 16. How is the ammeter connected in the circuit?
Ans. An ammeter is connected in series in the circuit.
Que 17. Why is an ammeter connected in series in an electric circuit?
Ans. It is connected in series so that whole of electric current, which it has to measure, passes through it.
Que 18. Name two devices in which electricity is converted into heat.
Ans. Electric heater and electric iron.
Que 19. Name the alloy which is used for making the filament of bulbs.
Ans. Tungsten.
Que 20. Name the instrument used for measuring potential difference.
Ans. Voltmeter is used for measuring potential difference.
Que 21. Name the instrument used for measuring electric current flowing in an electric circuit.
Ans. An ammeter.
Que 22. The following table gives the value of electrical resistivity of some materials:
|
Material |
Copper |
Silver |
Constantan |
|
Electrical resistivity (in Ω m) |
1.62 x 10-8 |
1.6 x 10-8 |
49 x 10-6 |
Which one of these materials is the best conductor of electricity?
Ans. Out of these three, silver has the lowest resistivity. Hence, silver is the best conductor of electricity.