Electric current - part (1)

Electric current – part (1)

Total Questions: 50

41. A device which converts electrical energy into mechanical energy is - [U.P.P.C.S. (Mains) 2007 Uttarakhand P.C.S. (Pre) 2005]

(a) Dynamo
(b) Transformer
(c) Electric motor
(d) Inductor

Correct Answer: (c) Electric motor

Solution:Electric motor is a device which converts electrical energy into mechanical energy. Electric motors involve rotating coils of wire which are driven by the magnetic force exerted by magnetic field or an electric current.

42. In electric motor : [64th B.P.S.C. (Pre) 2018]

(b) electrical energy is converted into heat.
(c) heat is converted into electrical energy.
(a) electrical energy is converted into mechanical energy.
(d) mechanical energy is converted into electrical energy.
(e) None of the above / More than one of the above.

Correct Answer: (a) electrical energy is converted into mechanical energy.

43. The device which works on the principle of electromagnetic induction is - [U.P. R.O/A.R.O. (Pre) 2011]

(a) Ammeter
(b) Voltmeter
(c) Dynamo
(d) Electric motor
(e) (c) & (d)

Correct Answer: (e) (c) & (d)

Solution:Among the above options, both Dynamo and Electric motor are such devices that work on the principle of electromagnetic induction. Dynamo converts mechanical energy inte electrical energy and electric motor converts electrical energy into mechanical energy.

44. A device which converts chemical energy into electrical energy is called - [R.A.S/R.T.S. (Pre) 2013]

(a) Battery
(b) Motor
(c) Generator
(d) Moving coil meter

Correct Answer: (a) Battery

Solution:An electrical battery is a device consisting of two or more electrochemical cell that converts stored chemical energy into electrical energy. There are different types of batteries but all have three basic components; a positive electrode, negative electrode, and electrolyte.

45. Electric motors operating at low voltages tend to burn out because- [U.P.P.C.S. (Pre) 2008]

(a) They draw more current which is inverse proportional to the voltage.
(b) proportional to the square root of the voltage.
(c) They draw heat proportional to v².
(d) Low voltage sets in electrical discharge.

Correct Answer: (a) They draw more current which is inverse proportional to the voltage.

Solution:Electric motors operating at low voltage tend to burn out because they have draw more current which is inversely inversely proportional to the voltage.

46. Faraday constant : [66th B.P.S.C. (Pre) 2020]

(a) depends on the amount of the electrolyte.
(b) depends on the current passed in the electrolyte.
(c) depends on the volume of the solvent in which the electrolyte is dissolved.
(d) is a universal constant.
(e) None of the above / More than one of the above.

Correct Answer: (d) is a universal constant.

Solution:The Faraday constant represents the magnitude of electric charge per mole of electrons. It is denoted by the symbol 'F' and is named after English scientist Michael Faraday. It is a universal constant. It has the currently accepted value F=96485.332123 C/mol .

47. Consider the following statements regarding a motor car battery- [I.A.S. (PRE) 1999]

1. The voltage is usually 12 V.
2. Electrolyte used is hydrochloric acid.
3. Electrodes are lead and copper.
4. Capacity is expressed in ampere-hour.
Which of the above statements are correct:

(a) 1 and 2
(b) 2 and 3
(c) 3 and 4
(d) 1 and 4

Correct Answer: (d) 1 and 4

Solution:A motor car battery usually has six 2V cells connected in series, which gives it a steady voltage of about 12V. The capacity of battery is expressed in ampere-hour. An ampere- hour is the total amount of electrical charge transferred when a current of one ampere flows for one hour.

Therefore the total usable charge stored in a battery can be stated in term of ampere-hour. The electrolyte used is a approx. 35% solution by weight of sulphuric acid H₂SO₄ with 65% of water. The electrodes used in motor car batteries are lead (Pb) and lead dioxide PbO₂.

48. Nickel-Cadmium (Ni-Cd) battery is used in: [Uttarakhand P.C.S. (PRE) 2016]

(a) calculator
(b) cordless electronic appliances
(c) transistor
(d) all of the above

Correct Answer: (d) all of the above

Solution:The nickel cadmium battery is a type rechargeable battery using nickel oxide hydroxide and metallic cadmium a electrodes, while potassium hydroxide is used as alkaline electrolyte. It is used in calculator, cordless electronic appliances, transistors, portable power tools, photography equipments, flashlight etc.

49. Of the two bulbs in the house one glow brighter than the other in this context which of the two has a larger resistance ? [U.P.P.C.S.(MAINS) 2017]

(a) the dim bulb.
(b) the brighter bulb.
(c) both have the same bulb.
(d) the brightness does not depend on the resistance.

Correct Answer: (a) the dim bulb.

Solution:The bulb which decays more energy will generate more brightness
power=voltage(V)×current(I)
it is known that V=I×Resistance (R)
P=V²/R ; P∝1/R thus the bulb of high resistance decays the low energy and will generate dim light.

50. What is the difference between a CFL and an LED Lamp? [I.A.S. (Pre) 2011]

1. To produce light, a CFL uses mercury vapour and phosphor while an material. LED lamp uses semi-conductor.
2. The average life span of a CFL is much longer than of an LED lamp.
3. A CFL is less energy-efficient as compared to an LED lamp.
Which of the statements given above is/are correct?

(a) 1 only
(b) 2 and 3
(c) 1 and 3
(d) 1, 2 and 3

Correct Answer: (c) 1 and 3

Solution:CFL uses mercury vapour and phosphor to produce light The gases becomes excited by electricity and when combined with mercury particles, produces invisible ultraviolet light. The UV light then hits the white phosphor coating inside the bulb causing it to fluorescence and emit white light.

LED lamp uses semi-conductor material to produce light. CFLs have a life of about 6000 to 10,000 hours, while LED has a life span of about 50,000 hours. LED lamps are more energy efficient as compared to CFL.

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Electric current – part (1)