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Questions Related to physics

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

The device which is used for converting electrical energy into mechanical energy is called:

  1. Electric motor

  2. Dynamo

  3. Transformer

  4. Battery
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A

An electric motor is an electrical machine that corrects electrical energy into mechanical energy. Working of electric motor mainly depends upon the interaction of magnetic field with current.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

The principle on which transformer works is?

  1. Mutual induction

  2. Self induction

  3. Electromagnetic induction

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.
Mutual inductance is where the magnetic field generated by a coil of wire induces voltage in an adjacent coil of wire. A transformer is a device constructed of two or more coils in close proximity to each other, with the  purpose of creating a condition of mutual inductance between the coils.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

The AC produced in India changes Its direction in every:

  1. $\displaystyle \frac{1}{100}$ second

  2. 100 second

  3. 50 second

  4. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

The rate at which alternating current reverses direction is called its frequency, expressed in hertz. Thus, standard household current in India is 50 Hz. AC electricity alternates back-and-forth in direction 50 times per second, according to the electrical system in the country. The charge at the ends of the wire alternates between negative (-) and positive (+). If the charge is negative (-), that pushes the negatively charged electrons away from that terminal. If the charge is positive (+), the electrons are attracted in that direction. Thus the electricity in the wire moves in one direction for a short while and then reverses its direction when the generator armature is in a different position. The direction changes twice in each cycle so that change of direction takes place after every 1/100 second.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

A transformer:

  1. transforms energy

  2. transforms frequency

  3. transforms voltage

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Answer is C.

Transformers are capable of either increasing or decreasing the voltage and current levels of their supply, without modifying its frequency, or the amount of Electrical Power being transferred from one winding to another via the magnetic circuit. So the current is sent through step up transformers to increase the voltage and to push the power over long distances.

Multiple choice physics electro-magnetism applications of electromagnets transformer transformers

A transformer is employed to ___________.

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

  2. convert D.C. into A.C.

  3. obtain a suitable A.C. voltage

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Answer is C.

Transformers are capable of either increasing or decreasing the voltage and current levels of their supply, without modifying its frequency, or the amount of Electrical Power being transferred from one winding to another via the magnetic circuit. So the current is sent through step up transformers to increase the voltage and to push the power over long distances.
Hence, transformer is employed to obtain a suitable A.C. voltage.

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.