Electric current – part (2)

Total Questions: 39

21. If potential difference and current flowing through a wire is increased twice each then electric power: [Chhattisgarh P.C.S. (Pre) 2015]

(a) Will remain unaffected
(b) Will increase four times
(c) Will increase two times
(d) Will decrease half

Correct Answer: (b) Will increase four times
Note:

Power P = V*I

where

V =Voltage

I = Current

Since both the voltage and current are increased twice Hence,

P'=(2V)(2I)

P' = 4V*I = 4P

the electric power will increase four times.

22. Given below are two statements, one labelled as [I.A.S. (Pre) 1996]

Assertion (A) and the other labelled as Reason (R).

Assertion (A): Transformer is useful for stepping up or stepping down voltages.

Reason (R) : Transformer is a device used in D.C. circuits.

In the context of the above two statements, which one of the following is correct?

(a) Both (A) and (R) are truc and (R) is the correct explanation of (A)
(b) Both (A) and (R) are true but (R) is not a correct explanation of (A)
(c) (A) is true but (R) is false
(d) (A) is false but (R) is true

Correct Answer: (c) (A) is true but (R) is false
Note:

A transformer transfers electric energy between two or more interconnected circuits through electric induction. It converts the high voltage to low voltage and low voltage to high and transmits it. Transformers can only function with alternating current (AC) not with direct current (DC)

23. Some pairs of devices and associated energy changes are given below: [R.AS/RTS(Pre) 2013]

(1) Electric generator - Mechanical to electrical

(11) Electric motor-Electrical to mechanical

(iii) Diesel engine-Light to electrical

(iv) Solar cell-Chemical to mechanical

Which of the above pair's is/are correctly matched!

(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iv)
(d) (ii) and (iv)

Correct Answer: (a) (i) and (ii)
Note:

An electric generator is a device that converts mechanical energy obtained from an external source into electrical energy as the output. A motor converts clectrical energy s mechanical energy. A diesel engine is an internal-combustion engine in which heat produced by the compression of air in the cylinder is used to ignite the fuel. Solar (or photovoltaic) cells convert the sun's energy into electricity

24. The device used for converting alternating current to direct current is called - [Chhattisgarh P.C.S. (Pre) 2008 U.P.P.C.S. (Pre) 2006]

(a) Inverter
(b) Rectifier
(c) Transformer
(d) Transmitter

Correct Answer: (b) Rectifier
Note:

Rectifier is an electric device that converts alternating current (AC) to direct current (DC).Inverter is an electronic circuit that changes direct current (DC) to Alternating Current (AC).The transformer supply alternating current or electric power from power grid to those appliances which use different voltages.Transmitter is an electronic device which, with the aid of antenna produces electromagnetic signals/radio waves. Primarily it is used for radio, television and in other communication tools.

25. Alternating current is converted to direct current - [U.P. U.D.A./L.D.A. (Spl.) (Mains) 2010]

(a) By Dynamo
(b) By Motor
(c) By Transformer
(d) By Rectifier

Correct Answer: (a) By Dynamo
Note:

26. Assertion (A): In India, electricity distribution companies calculate the consumption of electricity in kWh. [M.P.P.C.S. (Pre) 2008]

Reason (R): Electrical system in India works at a frequency of 60 Hz.

(a) both (A) and (R) are individually true, and (R) is the correct explanation of (A).
(b) both (A) are (R) are individually true, but (R) is not a correct explanation of (A).
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.

Correct Answer: (c) (A) is true, but (R) is false.
Note:

50Hz frequency of power transmission is fixed in our country for normal operation of the power grid. In there an increase or decrease of 0.5 Hz is acceptable. But if it increases or decreases more than that limit, the grid gets failed. In India, electricity distribution companies calculate the consumption of electricity in kWh (units). Thus, (A) is true, but (R) is false.

27. A statement is followed by two arguments I and II Choose which of the argument/s is/are strong: Statement: Should all diesel engines be replaced by electric engines in trains? [Rajasthan P.C.S. (Pre) 2023]

Arguments:

I. Yes, diesel engine causes a lot of pollution.

II. No, India does not produce enough electricity to fulfil even the domestic needs.

(a) Neither argument I nor argument II is strong.
(b) Both of the arguments are strong.
(c) Only argument II is strong.
(d) Only argument I is strong.

Correct Answer: (d) Only argument I is strong.
Note:

All diesel engines should be replaced by electric engines in trains as diesel engine causes a lot of pollution. Thus, argument I is strong for the statement. While argument II is not strong for the statement.

28. Which of the following option represents the consumption of power in ascending order [U.P.P.C.S. (Pre) 1992]

(a) Television, fan, electronic press, electronic kettle
b) Television, fan, electronic kettle, electronic press
(c) Fan, television, electronic press, electronic kettle
(d) Electronic press, electronic kettle, fan, television

Correct Answer: (c) Fan, television, electronic press, electronic kettle
Note:

Manufacturer of electronic equipment sets a power rating for every equipment which shows the maximum power that can be consumed by the specific device. According to the question, the ascending or increasing order of the electronic items by their power rating are fan, television, electronic press, electronic kettle.

29. Consider the following statements: [U.P.P.C.S.(pre) 2010]

Assertion (A): Space-based solar power (SBSP), it is suggested be made a national goal.

Reason (R) : Supply of SBSP is 99% uninterrupted throughout the year, besides the enormity of energy availability.

Select the correct answer using the codes given below:

Code:

(a) Both A and R are true, and R is the correct explanation of A.
(b) Both A and R are true, but R is not the correct explanation of A.
(c) A is true, but R is false.
(d) A is false, but R is true.

Correct Answer: (a) Both A and R are true, and R is the correct explanation of A.
Note:

Space-based solar power (SBSP) is a system for the collection of solar power in space for use on Earth. SBSP would differ from current solar collection methods in such a way that the means used to collect energy would reside on an orbiting satellite instead of the Earth's surface. The power is then transmitted via electromagnetic waves at 2.45 GHz to dedicated receiver stations on Earth. "Rectenna" convert the electromagnetic energy into electricity which is used in the local grid. The supply of SBSP will be 99% uninterrupted throughout the year besides the enormity. Former president Dr. APJ Abdul Kalam suggested that the space-based solar power (SBSP) should be made a national goal.

30. With reference to technologies for solar power production, consider the following statements: [I.A.S. (Pre) 2014]

1. 'Photovoltaics' is a technology that generates electricity by direct conversion of light into electricity, while 'Solar Thermal' is a technology that utilizes the Sun's rays to generate heat which is further used in electricity generation process.

2. Photovoltaics generates Alternating Current (AC), while Solar Thermal generates Direct Current (DC).

3. India has manufacturing base for Solar Thermal Technology, but not for Photovoltaics.

Which of the statements given above is/are correct?

(a) 1 only
(b) 2 and 3 only
(c) 1, 2 and 3
(d) None

Correct Answer: (a) 1 only
Note:

Photovoltaics refers to a technology which converts light into electricity using semiconducting materials that exhibit photovoltaic effect. Solar cells produce direct current electricity from sunlight. On the other hand, Solar Thermal Technology works on the principle of converting solar energy into heat energy by absorbing it which can be further used for electricity generation.In March, 2013 Ministry of New and Renewable Energy, Government of India informed that India has capacity of generating 2000 MW electricity through solar photovoltaic modules. This clarifies that India has infrastructure for photovoltaic technology.

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Electric current – part (2)