Physics

Electrical Machines and Circuits

754 Questions

Electrical machines and circuits involve the principles of alternating and direct current, transformers, diodes, and power consumption. These concepts are essential for engineering and technical exams. Review these practice questions to test your knowledge of circuit analysis.

Transformers and impedanceAlternating and direct currentCircuit components and diodesPower consumption calculations

Electrical Machines and Circuits Questions

Multiple choice physics household circuits electric switch switch electrical circuit

B). Solve the previous question if the closed loop is completely
enclosed. In the circuit containing the switch.

  1. An anticlockwise current-pulse

  2. A clockwise current-pulse

  3. An anticlockwise current-pulse and then an anticlockwise current-pulse

  4. A clockwise current-pulse and then an anticlockwise current-pulse
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics household circuits electric switch switch electrical circuit

In a household electric circuit

  1. all electric appliances drawing power are joined in parallel.

  2. a switch may be either in series or in parallel with the appliance which it controls.

  3. if a switch is in parallel with an appliance, it will draw power when the switch is in the 'off' position (open).

  4. if a switch is in parallel with an appliance, the fuse will blow (burn out) when the switch is put 'on' (closed).
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

In the household if the appliances are connected in series, if one appliance is turned off then the whole circuit breaks and all other will get turned off. So they are always connected in parallel so that we can use appliances independent of other.
The switch of an appliance must be connected in series because the purpose of a switch is to turn off/on (break and connect the circuit). So when we connect the switch in series, the appliance turn's on when switch is closed and off when open.
If the switch is connected in parallel, even when it is off(open) the appliance draws power and when it is on the terminals of the appliance gets shorted and blows the fuse.

Multiple choice physics household circuits electric switch switch electrical circuit

In an household electric circuit, which of the following is/are correct?
(A) All electric appliances drawing power are joined in parallel.
(B) A switch may be either in series or in parallel with the appliance which it controls.
(C) If a switch is in parallel with an appliance, it will draw power when the switch is in the 'off' position (open).
(D) If a switch is in parallel with an appliance, the fuse will blow (burn out) when the switch is put 'on' closed.

  1. A, D

  2. A, C, D

  3. B, C, D

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

In the household if the appliances are connected in series, if one appliance is turned off then the whole circuit breaks and all other will get turned off. So they are always connected in parallel so that we can use appliances independent of other.
The switch of an appliance must be connected in series because the purpose of a switch is to turn off/on (break and connect the circuit). So when we connect the switch in series, the appliance turn's on when switch is closed and off when open.
If the switch is connected in parallel, even when it is off(open) the appliance draws power and when it is on the terminals of the appliance gets shorted and blows the fuse.

Multiple choice physics household circuits electric switch switch electrical circuit

Switches of the electric appliances are connected in the _____ wire.

  1. neutral

  2. line

  3. earth

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

Each local circuit in a room is provided with a seperate switcho switches are connected in the live wire, so that when the switch is in the off portion, no point of the connected electric appliance will be at higher potential.

Multiple choice physics household circuits electric switch switch electrical circuit

In a household electric circuit:

  1. all electric appliances drawing power are joined in parallel

  2. a switch may be either in series or in parallel with the appliance which it controls

  3. if a switch is in parallel with an appliance, it will draw power when the switch in the off position (open)

  4. if a switch is in parallel with an appliance, the fuse will blow (burn out) when the switch is put on (closed)
Reveal answer Fill a bubble to check yourself
A,C,D Correct answer
Explanation

All appliances in houses are connected parallel so that even if one get damaged , others will work properly and all appliances are independent .
If switch is connected in parallel, there will be short circuit when  switch is on and hence fuse will be blown and when switch is off, the appliance will draw power and there won't be any short circuit.

Multiple choice physics household circuits electric switch switch electrical circuit

Of the three connecting wires in a household circuit : (i) Which of the three wires should the switch be connected ?

  1. Live

  2. Neutral

  3. Earth

  4. All of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Switch must be connected to the live wire so that it can disconnect the circuit when it is switched off.

Multiple choice physics electronic devices introduction to diodes circuit components junction diode and its voltage current characteristics

For the plate voltage, the plate current in a triode valve is maximum when the potential of :

  1. The gird is positive and plate is negative

  2. The grid is zero and plate is positive

  3. The grid is negative and plate is positive

  4. The grid is positive and plate is positive
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In a triode, the plate current is controlled by the grid potential. When both the grid and the plate are positive, they both attract electrons emitted from the cathode, maximizing the plate current.

Multiple choice physics electric circuits introduction to diodes circuit components junction diode and its voltage current characteristics

Select the correct statement from the following 

  1. a diode can be used as a rectifier

  2. a diode cannot be used as a rectifier

  3. the current in a diode is always proportional to the applied voltage

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

A diode allows current to flow in only one direction, which is the fundamental principle behind rectification, converting AC to DC.

Multiple choice physics when current flows precaution with the electrical circuit precautions to be taken while dealing with current electrical safety devices used to protect from shock of electric current

An electric shock may be caused by

  1. Poor insulation of wires.

  2. Touching the appliances with wet hands.

  3. No earthing of the appliance.

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

An electric shock may be caused from an appliance due to 
i) Poor insulation of wires,
ii) Touching the appliances with wet hands and 
iii) No earthing of the appliance.
To avoid it,the insulation of wires must be of good quality and it should be checked from time to time particularly when they become old,so that no wire is left naked the appliance should never be operated(or touched)with wet hands and they should always be kept dry.the appliances must have its metallic case earthed the appliances must be provided with a fuse.

A person can get an electric shock by touching it if the wire has poor insulation of rubber over it.
An electric shock may also be caused by touching the appliance that was either not earthed or touching it with wet hands.

Thus option D is correct.

Multiple choice physics when current flows precaution with the electrical circuit precautions to be taken while dealing with current electrical safety devices used to protect from shock of electric current

Mark the appropriate answer(options includes safety precautions to be used while using electricity)

  1. If water or a chemical is spilled onto equipment, shut off power at the main switch or circuit breaker and unplug the equipment.

  2. Equipment producing a tingle should be disconnected and reported promptly for repair.

  3. Do not rely on grounding to mask a defective circuit nor attempt to correct a fault by insertion of another fuse or breaker, particularly one of larger capacity

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

Safety precautions to be used while using electricity:

  1. If water or a chemical is spilled onto equipment, shut off power at the main switch or circuit breaker and unplug the equipment. Very logical. NEVER try to remove water or similar from equipment while energized. After all, it’s stupid to do so.
  2. Equipment producing a “tingle” should be disconnected and reported promptly for repair. 
  3. Do not rely on grounding to mask a defective circuit nor attempt to correct a fault by insertion of another fuse or breaker, particularly one of larger capacity.

Multiple choice physics when current flows precaution with the electrical circuit precautions to be taken while dealing with current electrical safety devices used to protect from shock of electric current

What are the possible risk when an electrical appliance is used in wet places?

  1. The fuse blows

  2. The user gets an electric shock

  3. Fire occurs

  4. Appliance gets over heated
Reveal answer Fill a bubble to check yourself
B,C Correct answer
Explanation

User will get shock as water is good conductor of electricity .When water gets into the appliance, it may get into contact with live wire and conduct the charge out of live wire to user.

It can cause fire ,as water is good conductor of current.It can cause short circuit and very high current can cause heating or fire.