QUESTIONS ELECTRIC CURRENT

Electric Current

1. What is the SI unit of electric current ?

Ans: Ampere (A)

2. How can we measure electric current?

Ans: Usually Ammeter is used to measure electric current.

3. How can we connect Ammeter to the circuit ?

Ans: Ammeter is always connected in series to the circuit.

4. What is the SI unit of potential difference

Ans: Volt (V)

5. How can we measure potential difference or emf ?

Ans: Volt meter is used to measure potential difference or emf.

6. How can we connect volt meter to the electric device ?

Ans: Volt meter must be connected in parallel to the electric device.

7. Do you know the voltage of mains that we use in our household circuits ?

Ans: 240 V

8. What happens to the resistance of a conductor if we increase its length ?

Ans: Increase

9. What is the SI unit of emf (Electromotive force)

Ans: Volt

10. What is the SI unit of resistance ?

Ans: ohm (Ω)

11. What is the SI unit of resistivity ?

Ans: Ω - m

12. What is Conductivity ?

Ans: Conductivity: The reciprocal of resistivity is called

13.is the symbol of

 A) Battery B) Rheostat C) Resistance D) Ammeter

 Ans: C) Resistance

14. The specific resistance does not change, if

 A) The material is changed. B) The temperature is changed.

 C) The shape of the resistor is changed. D) Both material and temperature are changed

Ans: C) The shape of the resistor is changed.

15. A thick wire has --------------- resistance than a thin wire.

 A) more B) less C) equal D) Both A and B

Ans: B) less

16. A circuit draws a current of 2A from a 12 V battery, its resultant resistance is --------------

 A) 12 Ω B) 2 Ω C) 6 Ω D) 18 Ω

Ans: C) 6 Ω

17. Find the incorrect statement/ statements from the following:

 i) Resistance of a conductor depends on material.

ii) Resistance of a conductor independent of area of cross section.

iii) Resistance of a conductor depends on its length.

iv) Resistance of a conductor is independent of its temperature.

 A) (i) & (ii) B) (ii) & (iii) C) (ii) & (iv) D) (i) & only (iv)

Ans: C) (ii) & (iv)

18. Which one of the following is the correct procedure to measure potential difference ?

 A) Connecting a voltmeter in parallel in the circuit

 B) Connecting a voltmeter in series in the circuit

 C) Connecting an ammeter in parallel in the circuit

 D) Connecting an ammeter in series in the circuit

Ans: A) Connecting a voltmeter in parallel in the circuit

19. Which one of the following is the correct match pair ?

i) Ammeter ( ) a) Connected parallel in the circuit

ii) Tap key ( ) b) Connected series in the circuit

iii) Voltmeter ( ) c) Used to attach and detach the circuit

 A) i-a, ii-b; iii-c B) i- b, ii-c, iii–a C) i-c, ii-a, iii-b D) i-a, ii–c, iii-b

Ans: B) i- b, ii-c, iii–a

20. Potential difference is measured with ………..

 A) Ammeter B) Galvanometer C) Battery D) Voltmeter

Ans: D) Voltmeter 

1. What is Electric current ?

Ans: Electric current: 1. Electric current is defined as the amount of charge crossing any cross section of

 the conductor in one second.

 Electric current (I) = Q/t

2. Define Ohm’s law.

Ans: Ohm’s law: At constant temperature, the potential difference between the ends of a conductor is directly

 proportional to the electric current passing through it.

 V = IR

3. Why do we consider tungsten as a suitable material for making the filament of a bulb ?

Ans: We consider tungsten as a suitable material for making filament of the bulb because,

1. It has high resistivity value (5.60 ×10-8 Ω-m).

2. It has high melting point (3422oC).

4. Silver is a better conductor of electricity than copper. Why do we use copper wire for

 conduction of electricity ?

Ans: 1. Silver is a better conductor of electricity than copper.

2. But silver is a costly metal than copper.

3.Copper can be made in to wires easily than silver

4. Hence copper is widely used for conduction for electricity.

5. Define potential difference or Voltage.

Ans: Potential difference or Voltage: Work done by the electric force on unit positive charge to move it through a distance 'l'  from A to B is called potential difference between those points or voltage.

 V = W/q = Fe l/q

6. What is emf ?

Ans: emf (Electromotive force): The work done by the chemical force to move unit positive charge from  negative terminal to positive terminal of the battery is called emf.

 ε = W/q = Fed/q

7. Define volt.

Ans: Volt: If 1 Joule work is done to move 1 coulomb of positive charge from one point to another, then the potential difference between those two points is 1 ‘volt’.

 1 volt = 1 Joule/ 1 coulomb

8. What is resistance ?

Ans: Resistance: The resistance of a conductor is defined as the obstruction to the motion of the electrons in a conductor.

9. What is a resistor?

Ans: Resistor : The material which offers resistance to the motion of electrons is called resistor.

10.Name the factors that affecting the resistance of a material?

Ans: The factors that affecting the resistance of a material are,

1. Temperature.

2. Nature of the material.

3. Length of the conductor.

4. Area of cross section.