Tag: electro-magnetism

Quizzes (12) Questions (113)

Questions Related to electro-magnetism

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

A transformer is

  1. A device for stepping up D.C.

  2. A generator of current

  3. Device for converting direct current into alternating current

  4. A device for stepping up or down the voltage of A.C. supply
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 A transformer is a device that is used to either raise or lower voltages and currents in an electrical circuit. In modern electrical distribution systems, transformers are used to boost voltage levels so as to decrease line losses during transmission

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

The best material for the core of a transformer is:

  1. Stainless steel

  2. Mild steel

  3. Hard steel

  4. Soft iron
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Answer is D.

Soft iron are ferromagnetic materials made of iron which can be magnetized and demagnetized easily. This is an advantage in transformers because in transformers, we're constantly varying magnetism of the core. This is important because without the change of magnetism of the core, there wouldn't be any voltage induced in the second circuit (the output)! Hence, using a soft iron would allow the magnetism of the core to be changed easily, lessening the amount of energy lost and increasing the efficiency of the transformer. 
Hence, soft iron is used to make core of the transformer.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

The best material for the core of a transformer is

  1. mild steel

  2. stainless steel

  3. soft iron

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

Soft iron provides the best material for the core of a transformer as its permeability $(\mu)$ is very high. Its hysteresis curve is of small area and its coercivity is very low.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

In a step-up transformer, the turns ratio is $5 : 1$. The primary is connected to a battery of emf $10 V$. The voltage across secondary is ________.

  1. $50 V$

  2. $100 V$

  3. $25 V$

  4. Zero
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Transformer works only for alternating current because there will be no flux linked with the coil of transformer as the voltage is constant.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

A transformer works on the principle of __________.

  1. self-induction

  2. electrical inertia

  3. magnetic effect of electric current

  4. mutual induction
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A transformer consists of a primary coil and the secondary coil. The current from the primary coil is induced into the secondary coil. Since there is the involvement of two coils mutually, it is termed as mutual induction.

A transformer works on the principle of mutual induction.

Option $(D)$ is correct.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

A transformer

  1. Converts AC to DC

  2. Converts DC to AC

  3. Increases or decreases (step up or step down) AC voltage

  4. Increases or decreases (step up or step down) DC voltage
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

C

Transformer is a static device which transforms electrical energy from one circuit to another and with the help of mutual inductor between two windings. The transformer may be step up or step down. A transformer that increases voltage from primary to secondary (more secondary windings turns than primary winding turns) is called step up transformer. Conversely a transformer designed to do just the opposite is called step down transformer. 

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

The purpose of a transformer is to do which of the following?

  1. Change voltage

  2. Reduce resistance

  3. Decrease heat transfer

  4. Increase magnetic fields

  5. Reverse current flow
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A transformer is based on the principle of mutual inductance , and it is used to change the alternating voltage . The transformer which increases the voltage is called step-up transformer , and which decreases is step-down transformer .

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

Complete the given statement, in order for a transformer to work:

  1. the magnetic field must be changing.

  2. the magnetic field must not change.

  3. it must be connected to a direct current source.

  4. the primary coil and the secondary coil must have different numbers of turns.

  5. the number of turns in the secondary coil must be greater than the number of turns in the primary coil.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The transformer works on the principle of mutual induction. The voltage in one coil changes to change the magnetic field that it creates. This changing magnetic field causes a flux change in the secondary coil, which would create an induced emf in the coil. Thus it is necessary to have a changing magnetic field in a transformer to cause induction in secondary coil.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

Fill the vacant spaces with appropriate terms. The _______ going into a transformer is equal to the _______ going out of the transformer.

  1. power, voltage

  2. power, power

  3. current, current

  4. voltage, voltage

  5. voltage, power
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Working of transformer is based on the conservation of power i.e no power is lost inside the transformer.

Thus total power going into a transformer is equal to the total power going out of the transformer.