Electric Current (Physics) Part-II

Total Questions: 39

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

Correct Answer: (d) By Rectifier
Solution:

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.

22. 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.

Code:

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

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.

23. A statement is followed by two arguments I and II. Choose which of the argument's is/are strong: [Rajasthan P.C.S. (Pre) 2023]

Statement: Should all diesel engines be replaced by electric engines in trains?

Arguments:

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

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

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

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.

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

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

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.

25. The Earth's magnetic field is due to: [U.P.P.C.S. (Mains) 2011]

Correct Answer: (a) Currents circulating inside the core
Solution:

The Earth's magnetic field is believed to be generated by electric currents in the conductive material of its core, created by convection currents due to heat escaping from the core.

26. What is the source of electrical energy in an artificial satellite? [U.P.P.C.S. (Pre) 2014, 2006, 2000, M.P.P.C.S. (Pre) 2000]

Correct Answer: (a) Solar cells
Solution:

In artificial satellites solar (or photovoltaic) cells convert the Sun's energy into electrical energy through photovoltaic effect. The photovoltaic effect is the creation of voltage and electric current in a material upon exposure to light.

27. 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:

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

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.

28. 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?

Correct Answer: (a) 1 only
Solution:

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.

29. With reference to solar water pumps, consider the following statements: [I.A.S. (Pre) 2020]

1. Solar power can be used for running surface pumps and not for submersible pumps.

2. Solar power can be used for running centrifugal pumps and not the ones with piston.

Which of the statement given above is/are correct?

Correct Answer: (d) Neither 1 nor 2
Solution:

Solar-powered pumps run on electricity generated by photovoltaic panels or the radiated thermal energy available from collected sunlight as opposed to grid electricity or diesel run water pumps.

Solar power can be used for running surface pumps as well as for submersible pumps. Solar-powered submersible pumps support varied applications like field irrigation or supply potable water, while drawing water from underground water sources like bore-wells or sumps.

Some solar submersible pumps use the same centrifugal mechanism as a surface pump, while others use a positive displacement mechanism.

A solar-powered reciprocating pump is class of positive displacement pump with piston, which is used for various purposes such as, car washing, irrigation, colour spraying, large fountain, garden water pump etc. From the above explanation it is clear that both of the given statements are incorrect.

30. Which one of the following elements is used in solar cells? [Uttarakhand P.C.S. (Pre) 2012]

Correct Answer: (a) Silicon
Solution:

Solar cells are the components of solar arrays that convert radiant light from the sun into electricity that is then used to power electrical devices. Solar cells contain materials with semiconducting properties in which their electrons become excited and turned into an electrical current when struck by sunlight.

While there are a dozen of variation of solar cells, the two most common types are those made of crystalline silicon (both monocrystalline and polycrystalline) and those made with what is called thin film technology. The majority (90%) of the solar cells on the market today are made of silicon.