Large transformers, when used for some time, become very hot and are cooled by circulating oil. The heating of the transformer is due to

A) the heating effect of current alone
B) hysteresis loss alone
C) both the heating effect of current and hysteresis loss
D) intense sunlight at noon

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out of the following, which is not emitted by radioactive substance?

A) Electrons
B) Electromagnetic radiations
C) Alpha particles
D) Neutrons

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Rectifiers are used to convert

A) Direct current to Alternating current
B) Alternating current to Direct current
C) high voltage to low voltage
D) low voltage to high voltage

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Sound waves in air are

A) transverse
B) longitudinal
C) electromagnetic
D) polarised

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It is easier to roll a stone up a sloping road than to lift it vertical upwards because

A) work done in rolling is more than in lifting
B) work done in lifting the stone is equal to rolling it
C) work done in both is same but the rate of doing work is less in rolling
D) work done in rolling a stone is less than in lifting it

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