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Worksheet on Current electricity

Q1 The current in a conductor varies with time t as I = 2t + 3t to the power (2) A where I is amperes and t in seconds. Electric charge flowing through a section of the conductor during t = s to t = 3 s is :-


a) 10 C

b) 24 C

c) 33 C

d) 44 C



Q2 10,000 electrons are passing per minute through a tube of radius 1cm. The resulting current is :


a) 10000 A

b) 0.25 x 10 to the power (-16) A

c) 10 to the power (-9) A

d) 0.5 x 10 (-19) A



Q3 S.I. unit of current is :-


a) C

b) A

c) A/s

d) N/s



Q4 When no current flows through a conductor :-


a) the free electrons do not move

b) the average speed of a free electron over a large period of time is zero

c) the average velocity of a free electron over a large period of time is zero

d) the average of square of velocities of all the free electrons at an instant is zero



Q5 A steady current flows in a metallic conductor of non-uniform cross-section. The quantity/quantities which remain constant along the length of the conductor is/are.


a) current, electric field and drift velocity

b) drift speed only

c) current and drift speed

d) current only



Q6 The electric resistance of a certain wire of iron is R. If its length and radius both are doubled, then :-


a) the resistance will be halved and the specific resistance will remain unchanged

b) the resistance will be halved and the specific resistance will be doubled

c) the resistance and the specific resistance, will both remain unchanged

d) the resistance will be doubled and the specific resistance will be halved.



Q7 When a piece of aluminium wire of finite length is drawn to reduce its diameter to half its original value, its resistance will become :-


a) two times

b) four times

c) eight times

d) sixteen times



Q8 As the temperature of a metallic resistor is increased, the product of resistivity and conductivity :-


a) increases

b) decreases

c) may increase or decrease

d) remains constant.



Q9 The length of a given cylindrical wire is increased by 100%. Due to the consequent decrease in diameter the change in the resistance of the wire will be :-


a) 300%

b) 200%

c) 100%

d) 25%



Q10 On increasing the temperature, the specific resistance of a conductor and a semiconductor-


a) both increase

b) both decrease

c) increases and decreases respectively

d) decreases and increases respectively



Q11 Specific resistance of a conductor increases with :-


a) increase in temperature.

b) increase in cross-sectional area

c) increase in cross-sectional area and decrease in length.

d) decrease in cross-sectional area.



Q12 The temperature coefficient of resistance of a wire is 0.00125 per degree celsius. At 300 K its resistance is 1 ohm. The resistance of the wire will be 2 ohms at a temperature :-


a) 1154 K

b) 1127 K

c) 600 K

d) 1400 K



Q13 Resistance in the two gaps of a meter bridge are 10 ohms and 30 ohms respectively. If the resistances are interchanged, the balance point shifts by :-


a) 33.3 cm

b) 66.67 cm

c) 25 cm

d) 50 cm



Q14 Potentiometer is used for measuring :


a) potential difference

b) current

c) internal resistance

d) All of these



Q15 Length of a potentiometer wire is kept long and uniform to achive :-


a) uniform and more potential gradient

b) non-uniform and more potential gradient

c) uniform and less potential gradient

d) non-uniform and less potential gradient



Q16 The sensitivity of a potentiometer is increased


a) increasing the emf of the cell.

b) increasing the length of the potentiometer wire

c) decreasing the length of the potentiometer wire

d) none of the above.



Q17 A potential gradient is established in the wire by a standard cell for the comparison of emf's of two cells in a potentiometer experiment. Which possibility of the following will lead to the failure of the experiment?


a) the emf of the standard cell is higher than that of the other cells.

b) the diameter of the wire is equal along its length

c) the number of wires is ten.

d) the emf of the standard cell is less than that of either cells



Q18 Consider the following two statements :

(A) Kirchhoff's junction law follows from the conservation of charge.

(B) Kirchhoff's loop law follows from the conservation of energy.

Which of the following is correct?


a) Both (A) and (B) are correct

b) Both (A) and (B) are wrong

c) (A) is correct and (B) is wrong

d) (A) is wrong and (B is correct.



Q19 The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length, its new resistance will be :-


a) R/n

b) n to the power (2) R

c) R/n to the power (2)

d) nR



Q20 A potentiometer is an accurate and versatile device to make electrical measurements of E.M.F. because the method involves :-


a) Potential gradients

b) A condition of no current flow through the galvanometer

c) A combination of cells, galvanometer and resistances

d) Cells



Q21 When a potential difference is applied across the ends of a linear metallic conductor :-


a) group of free electrons are accelerated continuously from the lower potential end to the higher potential end of the condcuctor

b) group of free electrons are accelerated continuously from the higher potential end to the lower potential end of the conductor

c) group of free electrons aquire a constant drift velocity from the lower potential end to the higher potential end of the conductor.

d) each free electron is set in motion from their position of rest.



Q22 Assertion : Electric field inside a current carrying wire is zero.

Reason : Net charge in a current carrying wire is non zero.


a) A

b) B

c) C

d) D



Q23 Assertion : A voltmeter must be connected in parallel in a circuit and it should have a high resistance.

Reason :The voltmeter in the circuit must not affect the potential difference measured by it.


a) A

b) B

c) C

d) D



Q24 Assertion : Electric field due to steady current carrying wire is zero outside the wire.

Reason : Net charge present in a current carrying wire is zero.


a) A

b) B

c) C

d) D



Q25 Assertion : Kirchhoff's voltage law indicates that electrostatic field is conservative.

Reason : Potential difference between two points in a circuit does not depend on path.


a) A

b) B

c) C

d) D



Q26 Assertion : Terminal potential difference of a cell is always less than its emf.

Reason : Potential drop due to internal resistance of cell increases the terminal potential difference.


a) A

b) B

c) C

d) D



Q27 Assertion : When wheatstone bridge is balanced, the current through the cell depends on the resistance of galvanometer.

Reason : In the balanced condition, current through the galvanometer is very high.


a) A

b) B

c) C

d) D



Q28 Assertion : Potentiometer measures the correct value of emf of a cell.

Reason : No current flows through the cell being balanced at the null point of potentiometer.


a) A

b) B

c) C

d) D



Q29 Assertion : When identical cells are connected in parallel to an external load, the effective e.m.f. increases.

Reason : All the cells will be sending unequal currents to the external load in the same direction.


a) A

b) B

c) C

d) D



Q30 Assertion : Potentiometer is an ideal instrument to measure the potential difference.

Reason : Potential gradient along the potentiometer wire can be made very small.


a) A

b) B

c) C

d) D



Q31 Assertion : Current is a scalar quantity.

Reason : Electric current arises due to continuous flow of charged particles or ions.


a) A

b) B

c) C

d) D



Q32 Assertion: Total current entering a circuit is equal to that leaving it by Kirchhoff's law.

Reason : It is based on conservation of energy.


a) A

b) B

c) C

d) D



Q33 Assertion : When a straight wire is bent to form L-shape, its resistance increases.

Reason : Electrons take longer time to travel along a bent wire as compared to travel along a straight wire.


a) A

b) B

c) C

d) D



Q34 Assertion :- As temperature of a metallic current carrying the wire is increased, its resistance increases.

Reason :- Decrease in temperature results in a decrease of electric field strength along the conductor so that the current reduces.


a) A

b) B

c) C

d) D



Q35 Assertion : The value of temperature coefficient of resistance is positive for metals.

Reason :The value of temperature coefficient of resistance is negative for insulators.


a) A

b) B

c) C

d) D



Q36 Assertion :- Two unequal resistances are connected in parallel across a cell, then current through the smaller resistance is more.

Reason :- In a parallel combination the potential difference will be the same.


a) A

b) B

c) C

d) D



Q37 Assertion :- EMF of battery decreases with time.

Reason :- Internal resistance increases with time.


a) A

b) B

c) C

d) D



Q38 Assertion :- When we use new battery, it can give voltage near to its EMF.

Reason :- The internal Resistance of new cell is very low.


a) A

b) B

c) C

d) D


ANSWERS


1) b

2) b

3) b

4) c

5) d

6) a

7) d

8) d

9) a

10) c

11) a

12) b

13) d

14) d

15) c

16) b

17) d

18) a

19) b

20) b

21) c

22) d

23) a

24) a

25) a

26) d

27) d

28) a

29) d

30) b

31) b

32) c

33) d

34) c

35) b

36) a

37) b

38) a

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