Tag: physics

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Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

What will happen if the strip in a doorbell loses its flexibility?

  1. Striker may break if current is large.

  2. After hitting the metal gong, it never returns to original position and only a single sound is produced.

  3. System of doorbell breaks

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Because of lack of flexibility, striker will resist change of motion more and may break if current is large.

Without flexibility, no rebounding force is present and striker will not return to its original position.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

What is the use of flexibility strip in a doorbell?

  1. It brings back striker to its original position

  2. It supports the motion of the striker

  3. It completes the electric circuit flexibly

  4. Its a safety precaution
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Without the flexibility strip, the striker will not come back to original position when the electrical circuit breaks.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Electric doorbell

  1. Always consume power

  2. Consume power only when switch is pressed

  3. Do not consume power practically and needs only starting power

  4. cant say
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When switch is pressed, circuit completes and ringing begins. Hence, electrical energy is converted to sound energy. As switch is released, no current flows and no energy is consumed,

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Exposed Electric doorbell can be damaged by 

  1. Mechanical damage

  2. High Electric currents

  3. Humidity

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Mechanical Damage to metal gong or striker may hinder working of the bell.

High electric currents may cause heating and burning of electrical circuit.
Humidity may cause short circuit between two unconnected wires, causing high electric currents and damage.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

During a doorbell ringing

  1. Current always flows in the circuit

  2. Electromagnet is always present

  3. Striker is always in contact with metal gong

  4. Striker always repeatedly hits metal gong
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Striker repeatedly hits the metal gong when doorbell is ringing. 

This can be observed in regular bells used at homes.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Armature is pulled towards the spring when it strikes the gong because

  1. The electromagnet gets demagnetized

  2. The current flow breaks

  3. Spring effect

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The working of an electric magnet is based on the magnetic effect of current. When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature. This movement of the armature causes the hammer to strike the gong. However when the armature moves towards the gong the connection between the spring strip and adjusting screw is lost which breaks the circuit and the current flow is stopped thus demagnetizing the electromagnet. This causes the armature to return to its original position and it is thus pulled back due to the spring effect of the spring strip. This process is called a make and break circuit.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

Which process is applied on a circuit for the working of an electric bell?

  1. Magnetization

  2. Make and break

  3. Both A and B

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The working of an electric magnet is based on the magnetic effect of current. When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature. This movement of the armature causes the hammer to strike the gong. However when the armature moves towards the gong the connection between the spring strip and adjusting screw is lost which breaks the circuit and the current flow is stopped thus demagnetizing the electromagnet. This causes the armature to return to its original position and it is thus pulled back due to the spring effect of the spring strip. This process is called a make and break circuit.

Multiple choice physics current electricity and magnetism electric bell the magnetic effect of a current electromagnetic forces oersted experiment oersted's experiment magnetic field due to a straight current carrying conductor

The hammer hits the gong because

  1. It has electric charge

  2. It displays the spring effect

  3. It is attracted towards the electro-magnet

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The working of an electric magnet is based on the magnetic effect of current. When the key is pressed the circuit gets completed and current passes through it causing the electromagnet to get magnetized which in turn attracts the armature. This movement of the armature causes the hammer to strike the gong.

Multiple choice physics option c: imaging fibre optics basics optical fibre the critical angle, total internal reflection and optical fibre

Light of different colours propagates through air :

  1. with velocity of air

  2. with different velocity

  3. with velocity of sound

  4. with equal velocity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
  • The velocity of the light does not change in air it will be equal for all the colours
  • If there may some other medium like water etc velocity will be changed
  • But it remains equal in air
  • Hence the option D is the right answer