Electric Current (Physics) Part-I

Total Questions: 50

1. Current density is: [69ᵗʰ B.P.S.C. (Pre) 2023]

Correct Answer: (b) a vector quantity
Solution:

The amount of electric current travelling per unit cross-section area is called as current density and expressed in amperes per square meter. It is a vector quantity.

The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.

2. A 100 watt electric bulb is used for 10 hours. What will be the cost of electricity consumed, if the consumption cost is Rs. 5 per unit ? [R.A.S./R.T.S. (Pre) 2012]

Correct Answer: (a) Rs. 5
Solution:

Energy Consumption of 100 watt electric bulb which is used for 10 hours = 100 × 10

= 1000 watt hour

= 1 kilowatt hour

= 1 Unit.

According to question the cost of 1 unit of electricity - Rs 5.

3. If a bulb of 100 watt burns for 10 hours, the expenditure of electricity will be-

Correct Answer: (b) 1 unit
Solution:

Energy Consumption of 100 watt electric bulb which is used for 10 hours = 100 × 10

= 1000 watt hour

= 1 kilowatt hour

= 1 Unit.

According to question the cost of 1 unit of electricity - Rs 5.

4. 15 bulbs each of 200 watt capacity in a Silkyara tunnel are illuminated continuously for 24 hours. The consumption of electricity will be: [U.P.R.O/A.R.O. (Pre) 2023]

Correct Answer: (b) 72 units
Solution:

Consumption of electricity by one bulb

= (watt × hours)/1000

= (200 × 24)/1000

= 4.8 units

Hence, total consumption of electricity by 15 bulbs

= 15 × 4.8

= 72 units

5. Five bulbs each of 100 watt capacity in a tunnel are illuminated continuously for twenty hours. The consumption of electricity will be: [U.P.P.C.S. (Pre) 2017]

Correct Answer: (c) Ten units
Solution:

Consumption of electricity by one bulb

(No. of units) = (watt × hours)/1000

= (100 × 20)/1000

= units

Thus, consumption of electricity by 5 bulbs = 2 × 5

= 10 units

6. The value of 1 kilowatt hour is- [U.P.P.C.S. (Pre) 2006]

Correct Answer: (a) 3.6 × 10⁶ J
Solution:

1 Kilowatt hour = 1 (kilowatt) (1 hour)

= (1000 joule/sec.) (3600 sec.)

= 36 × 10⁵ Joule

= 3.6 × 10⁶ Joule

Thus, option (a) is correct.

7. An electric bulb of 100 watt is used for 4 hours. The unit of electric energy used is- [U.P. Lower Sub. (Pre) 2009]

Correct Answer: (d) 0.4
Solution:

The electric energy consumed = 100 watt × 4 hour

= 400 watt hour

= 400/1000 kilowatt hour

= 0.4 kilowatt hour

= 0.4 unit

8. Electricity consumption bill is based on the measurement of- [40ᵗʰ B.P.S.C. (Pre) 1995]

1. Watt

2. Voltage

3. Ohm

4. Ampere

Select your answer of the following codes -

Correct Answer: (a) Only 1
Solution:

Electricity consumption bill is based on the measurement of kilowatt hour. The kilowatt hour is the unit of electricity consumption, equal to 1000 watt in 1 hour (1 unit).

9. How many units of electricity will be consumed if you use a 60-watt electric bulb for 5 hours everyday for 30 days? [R.A.S/R.T.S. (Pre) 2003]

Correct Answer: (b) 9
Solution:

We know that-

Number of units = watt × hour/1000

= (60 × 30 × 5)/1000 = 9 unit

10. An electric bulb is connected to 220 v generator. The current is 0.5 A. The power of the bulb is [Chhattisgarh P.C.S. (Pre) 2016]

Correct Answer: (a) 110 w
Solution: