Tag: physics

Questions Related to physics

Hydrometers are used to serve what purpose?

physics forces in fluids hydrometer and lactometer comparing density - relative density principle of floatation and its applications

  1. For determining density of liquid

  2. Pressure measurement

  3. Viscosity measurement

  4. None of the above

Show answer
Correct Option: A
Explanation:

Answer is A

A hydrometer is an instrument used to measure the specific gravity (relative density) of liquids; that is, the ratio of the density of the liquid to the density of water. A hydrometer is usually made of glass and consists of a cylindrical stem and a bulb weighted with mercury or lead shot to make it float upright

The word "earthing" also implies:

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. charging of a body.

  2. discharging of a body.

  3. putting a body on the surface of earth.

  4. putting a body under the surface of earth.

Show answer
Correct Option: B
Explanation:
An earthing system or grounding system is circuitry which connects parts of the electric circuit with the ground, thus defining the electric potential of the conductors relative to the Earth's conductive surface.
Thus excess charge passes to the earth which is considered as infinite source of charge absorbent.i.e. charges are discharged.

Earthing is provided in buildings to protect it from:

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. lightning.

  2. leakage of electric current.

  3. cyclone.

  4. thunderstorm.

Show answer
Correct Option: B
Explanation:

Earthing is provided in the building to protect us from electrical shocks due to any leakage of electrical current. It is done to provide safety by minimizing the shock, if someone accidentally touches the faulty wire.

Which of the following statements is correct?

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. A wire with a green insulation is usually the live wire

  2. MCB works on the heating effect of current

  3. The earth wire should be connected to the body of an appliance

  4. A fuse should always be placed in the neutral wire ofa mains circuit

Show answer
Correct Option: C
Explanation:
Earth wire or Earthing connection in the electrical wiring at home is connected to a large capacity storage of metallic or salted materials.  These materials drain electric charge if it is present on the wire and make the charge/voltage potential on the wire to 0.

     Usually the metallic bodies of the electric appliances are connected to the Earthing in the 3-way plug connections.  If there is a surge in the electric power supply or if there is a short circuit some where, then the high voltage and the excess current flow in to the Earthing connection.  So the appliance is secure from damage.  

    If the electric wiring in the house or in the appliance is faulty and as a result, the metallic body of the appliance carries electricity/charge on it.  Then the high voltage or leaked charges flow in to the earth.  This saves us from electric shocks when we touch the appliances.

State whether true or false.
An earthing connection allows the excess electrons to flow into the earth.

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. True

  2. False

Show answer
Correct Option: A
Explanation:

An earthing connection allows the excess electrons to flow into earth. This statement is true. When a wire is attached between earth and conductor, excess electrons flow to earth leaving the conductor neutral.

The potential difference between live wire and neutral wire is

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. $100 V$

  2. $200 V$

  3. $50 V$

  4. None of these

Show answer
Correct Option: D
Explanation:

Potential difference between live wire and neutral wire is $220  V$.

In case of household circuit, earth wire is connected to

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. Input terminals of $kwh$ meter

  2. Body of the $kwh$ meter

  3. Both

  4. None

Show answer
Correct Option: B
Explanation:

Inside the house, the live and neutral wires are connected to the input terminals of $kwh$ meter, whereas earth wire is connected to body of $kwh$ meter.

If the insulation of live wire got damages and the live wire comes in contact with the metallic body of the appliance. When such electric appliance is connected to the mains, if not connected to the earth wire will also be raised to

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. $440 V$

  2. $110 V$

  3. $220 V$

  4. $600 V$

Show answer
Correct Option: C
Explanation:

Under these conditions if someone by chance happens to touch it then the person will get an electric shock.

What is the main purpose of earthing electrical appliances?

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. To present overloading

  2. To present short circuting

  3. To prevent the person form electric shock

  4. None of these

Show answer
Correct Option: C
Explanation:

In case of earthed appliances, if there is any leakage of current, or the live wire comes in contact with its body then the current flows to the ground through earth wire.

Earthing elements used can be

safety precautions to be taken while handling electricity electric charge and electric current physics ohm's law current electricity

  1. Copper wire

  2. Copper plate

  3. Salt

  4. All

Show answer
Correct Option: D
Explanation:

Earthing elements: Materials which are good conductors of electricity. Earthing elements are copper wire, copper plate, salt.