Tag: applications of electromagnets

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Questions Related to applications of electromagnets

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

State whether given statement is True or False
An autotransformer is one in which the primary and secondary are automatically coupled.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

An auto transformer is an electrical transformer with only one winding. The portion of the same winding acts both primary and secondary side of the transformer. 

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

In a transformer the number of turns in the primary coil is 200 and secondary coil is 600. The ratio between the electric current in the primary and secondary respectively is

  1. 1 : 4

  2. 4 : 1

  3. 1 : 3

  4. 3 : 1
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a transformer, we know that 
$\frac{V _2}{V _1}=\frac{N _2}{N _1}$
where $V _1$ and $V _2$ are voltage across primary and secondary coils respectively and $N _1$ and $N _2$ are respective number of turns. 

Also, the transformer doesn't add or take away energy, so the power in
the primary and secondary is equal:
$V _1I _1=V _2I _2$
Therefore, $\frac{I _1}{I _2}=\frac{N _2}{N _1}$ 
$\frac{I _1}{I _2}=\frac{600}{200}=\frac{3}{1}$ 
Hence, desired ratio is 3:1. (D)

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

Transformer works on.

  1. AC only

  2. DC only

  3. Both AC and DC

  4. AC more effectively than DC
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Transformer works on the principle of Electromagnetic induction i.e an emf is induced in the coil if the magnetic flux linked with the coil changes. Magnetic flux in the coil can change only in case of AC voltage supply. In case of DC voltage supply, magnetic flux in the secondary coil remains constant and thus no emf is induced in the secondary coil and so transformer cannot work in case of DC supply.
That's why, transformer can work on AC only.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

A transformer is employed to

  1. convert A.C. into D.C.

  2. covert D.C into A.C

  3. obtain a suitable A.C voltage

  4. obtain a suitable D.C voltage
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

C

A transformer is a device that is used to either raise or lower voltage, and currents in an electric circuit. Thereby, we can suitably obtain the voltage and current.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

Which of  the following has its working based on electromagnetic induction -

  1. Ammeter

  2. Voltmeter

  3. Transformer

  4. Galvanometer
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

C

Electromagnetic Induction is the production of an emf across an electrical conductor in aa changing magnetic field in a transformer the alternating current through the primary winding produces a continually changing flux and die to this alternating flux on emf is induced in the secondary winding.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

Read the following statements and answer whether the given statement is true or false.


A transformer is an electrical device that works on the principle of self-induction

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

False

A transformer consists of two electrically isolated coils and operates on Faraday’s principle of mutual induction, in which an EMF is induced in the transformer secondary coil due to the magnetic flux generated by the voltages and currents flowing in the primary coil working. In self induction there is only one coil and emf is induced in that coil due to the change in flux linked with that coil. 

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

A transformer works on both A.C. and D.C.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

False

Transformer does not work on DC. Direct current doesn’t have a variable magnetic field induced if fed through the primary winding of a transformer. Thus, only a constant magnetic field will act on secondary and shall not induce any voltage across the terminals of the same.