Tag: physics

Quizzes (598) Questions (13441)

Questions Related to physics

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

State whether True or False :

A transformer responds only to dc.

  1. True

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

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

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

State whether given statement is True or False
A transformer consists of two or more cores that are electrically coupled on a common core.

  1. True

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

A transformer consists of only single core and it has windings wound on the core which provides necessary magnetic field. The transformer may contain two or more windings.

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.