CBSE X Science Effects of Current - EducareHut (Next Gen Knowledge Point)

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#1. Which of the following gases are filled in electric bulbs?

Helium and Neon

Neon and Argon

Argon and Hydrogen

Argon and Nitrogen

#2. Two wires of same length and area, made of two materials of resistivity ρ1 and ρ2 are connected in parallel V to a source of potential. The equivalent resistivity for the same length and area is

Explanation: (b) Equivalent resistance in parallel combination is

1/R_P =1/R₁ 1/R₂

For the same length and area of cross-section, R ∝ p (resistivity)

#3. The resistivity of insulators is of the order of

10^-8 Ω-m

10^1 Ω-m

10^-6 Ω-m

10^6 Ω-m

#4. The resistance of hot filament of the bulb is about 10 times the cold resistance. What will be the resistance of 100 W-220 V lamp, when not in use?

48 Ω

400 Ω

484 Ω

48.4 Ω

R= V^2/P

#5. What is the maximum resistance which can be made using five resistors each of 1/5 Ω?

1/5 Ω

10 Ω

5 Ω

1 Ω

Explanation: The maximum resistance is obtained when resistors are connected in series combination.

Thus equivalent resistance obtained by connecting five resistors of resistance 1/5 Ω each, in series = (1/5 1/5 1/5 1/5) = 1 Ω

#6. In an electrical circuit, two resistors of 2 and 4 respectively are connected in series to a 6V battery. The heat dissipated by the 4 resistor in 5s will be

10J

20J

30J

Explanation:

Here, first resistor, R1 = 2Ω

And second resistor, R2 = 4Ω

Voltage of cell, V = 6V

Time taken = t = 5s

Total resistance of the circuit = R = R1 R2 = 2 4 = 6 Ω

Current, I = V/R = 6/6 = 1A

Heat dissipated by the 4Ω resistor in 5s is given as,

H = I²Rt

⟹ H = 1 x 1 × 4 × 5 = 20J

#7. A battery of 10 volt carries 20,000 C of charge through a resistance of 20 Ω. The work done in 10 seconds is

2 × 10^3 joule

2 × 10^5 joule

2 × 10^4 joule

2 × 10^2 joule

Explanation: (b) W= qV= 20000 × 10 = 2,00,000 = 2 × 10⁵ J

#8. Two devices are connected between two points say A and B in parallel. The physical quantity that will remain the same between the two points is

Current

Voltage

Resistance

None of these

Explanation:(b) In parallel combination, voltage remains same across two points.

#9. Three resistors of 1 Ω, 2 ft and 3 Ω are connected in parallel. The combined resistance of the three resistors should be

greater than 3 Ω

less than 1 Ω

equal to 2 Ω

between 1 Ω and 3 Ω

#10. Identify the circuit in which the electrical components have been properly connected.

iii

Explanation: Essential conditions are necessary when electrical components are connected

Voltmeter should be connected in parallel.
Ammeter is always connected in series.
Positive terminals of voltmeter and ammeter should be connected to positive terminal of the cell and their negative terminals should be joined to the negative terminal of the cell.

Thus, the above conditions are satisfied in case (ii).

#11. The effective resistance between A and B is

4Ω

6Ω

May be 10 Ω

Must be 10 Ω

Answer: a

Explanation: (a) 6 Ω is shorted so effective resistance is 4 Ω.

#12. In an electrical circuit three incandescent bulbs. A, B and C of rating 40W, 60 W and 100 W, respectively are connected in parallel to an electric source. Which of the following is likely to happen regarding their brightness?

Brightness of all the bulbs will be the same

Brightness of bulb A will be the maximum

Brightness of bulb B will be more than that of A

Brightness of bulb C will be less than that of B

Explanation: We know that power is defined as rate of doing work. A bulb consumes electric energy and produces heat and light. Now, bulb with more power rating will produce more heat and light or we can say that

Power rating of bulb is directly proportional to the brightness produced by bulb.

Therefore, brightness of bulb B with power rating 60 W will be more than the brightness of bulb A having power rating as 40W.

#13. A coil in the heater consume power P on passing current. If it is cut into halves and joined in parallel, it will consume power

P/2

#14. If R1 and R2 be the resistance of the filament of 40 W and 60 W respectively operating 220 V, then

R1 < R2

R2 < R1

R1 = R2

R1 ≥ R2

Explanation: (b) Using power, P = V^2/R or R = V^2/P

For the same voltage, R ∝ 1/P

More the power, lesser the resistance.

Accordingly, R2 < R1

#15. A fuse wire repeatedly gets burnt when used with a good heater. It is advised to use a fuse wire of

more length

less radius

less length

more radius

Explanation: (d) In order to get the working of heater properly, fused wire of higher rating must be used.

#16. The electrical resistance of insulators is

high

low

zero

infinitely high

#17. A current of 1 A is drawn by a filament of an electric bulb. Number of electrons passing through a cross-section of the filament in 16 seconds would be roughly

10^20

10^16

10^18

10^23

Explanation: (a) Q = ne and Q = It

∴ ne = It

n=IT/e= (1×16)/(1.6×10^-19)

10²⁰

#18. Two resistors are connected in series gives an equivalent resistance of 10 Ω. When connected in parallel, gives 2.4 Ω. Then the individual resistance are

each of 5 Ω

6 Ω and 4 Ω

7 Ω and 4 Ω

8 Ω and 2 Ω

Explanation: (b) In series, Rs = R₁ R₂ = 10 Ω

1/Rp = 1/4 1/6=2.4 Ω

#19. 1 mV is equal to:

10 volt

1000 volt

10^-3 volt

10^-6 volt

#20. Electrical resistivity of any given metallic wire depends upon

its thickness

its shape

nature of the material

its length

#21. Coulomb is the SI unit of:

Charge

Current

Potential difference

Resistance

#22. A cooler of 1500 W, 200 volt and a fan of 500 W, 200 volt are to be used from a household supply. The rating of fuse to be used is

2.5 A

5.0 A

7.5 A

10 A

Explanation: (d) Total power used, P = P₁ P₁ = 1500 500 = 2000 W.

Current drawn from the supply,I=P/V=2000/200=10A

#23. The resistance whose V-I graph is given below is

Explanation: (b) Resistance = slope line of V-I graph =

(9-0)/(15-0)=9/15=3/5

#24. Two resistors of resistance 2 and 4 when connected to a battery will have

same current flowing through them when connected in parallel

same current flowing through them when connected in series

same potential difference across them when connected in series

different potential difference across them when connected in parallel

Explanation: In series combination of resistor, the current through both the resistor are same but potential difference across each will be different.

In parallel combination, current across each resistor will be different but the potential difference will be same.

#25. What is the commercial unit of electrical energy?

Joules

Kilojoules

Kilowatt-hour

Watt-hour

Finish