A current of 0.6 A is drawn by an electric bulb for 10 minutes. Which one of the following is the amount of electric charge that flows through the circuit?
- A.6 C
- B.0.6 C
- C.360 C
- D.36 C
Correct answer
Explanation
The correct answer is C, 360 C. Electric charge equals current multiplied by time, Q = I × t, with time in seconds: 0.6 A × 600 s = 360 coulombs. Electric current is the rate at which charge flows through a conductor. One ampere means one coulomb of charge passing a point every second, so the coulomb is the same as an ampere-second. The key step in such questions is to convert the time to seconds: 10 minutes is 10 × 60 = 600 seconds. One coulomb is the charge of about 6.25 million million million (6.25 × 10^18) electrons. Option A is wrong because 6 C is what you get by multiplying 0.6 by 10, using minutes instead of seconds. Option B is wrong because 0.6 C is the charge that flows in just one second. Option D is wrong because 36 C would flow in one minute (0.6 × 60), not in ten minutes. Exam tip: Q = I × t, always in seconds; 1 C = 1 A × 1 s.
Practice Questions
View allThe rate of evaporation of liquid does not depend upon
- A.temperature
- B.its surface area exposed to the atmosphere
- C.its mass
- D.humidity
Show answer
Evaporation is a surface process, so its rate depends on conditions at the surface of the liquid, not on how much liquid there is in total.
Read the full explanation →Which one of the following is considered as a compound ?
- A.Silicon
- B.Tin
- C.Sugar solution
- D.Calcium carbonate
Show answer
Calcium carbonate, CaCO3, is a compound because calcium, carbon and oxygen are chemically combined in it in a fixed ratio.
Read the full explanation →'Altitude sickness' is caused at high altitude due to
- A.high partial pressure of oxygen
- B.low partial pressure of oxygen
- C.low level of haemoglobin
- D.high partial pressure of carbon dioxide
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As one climbs, air pressure falls, so each breath delivers oxygen at a lower partial pressure and less of it passes from the lungs into the blood.
Read the full explanation →Which one of the following is not a characteristic of a compound?
- A.Composition is variable.
- B.All particles of compound are of only one type.
- C.Particles of compound have two or more elements.
- D.Its constituents cannot be separated by simple physical methods.
Show answer
A compound always has a fixed composition by mass, so a variable composition is a property of mixtures, not compounds.
Read the full explanation →A positively charged particle (alpha-particle) is projected towards west in a horizontal plane. It is deflected towards north in the same plane by a magnetic field. Which one among the following is the direction of the magnetic field?
- A.Towards south
- B.Towards east
- C.Vertically downwards
- D.Vertically upwards
Show answer
The magnetic force on a moving charge is F = q(v × B), and only an upward field turns a westward-moving positive charge towards the north.
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