Physics [1 Mark Question Answer]

When no current is drawn from the cell i.e. when the cell is in open circuit, the potential difference between the terminals of the cell is called its electromotive force (or e.m.f).

No, a transformer cannot work on a d.c. source. With a d.c. source, there will be no change in magnetic flux linked with the secondary coil.

A transformer works on the principle of electromagnetic induction.

'kilowatt-hour' is the commercial unit of electricity. One kilo-watt hour is the electrical energy consumed by an electrical appliance of power 1 kW when it is used for 1 hour. 

Maximum power that can be taken, P =VI = 240 x 5 = 1200 w.

A fuse wire shou Id have high resistance and low melting po int.

No, we cannot find out the magnitude of current using Fleming's right hand rule; we can find only the direction of induced current.

(i) Fleming's left hand rule is used to find out the direction of Lorentz force on a conductor. (ii) Fleming's right hand rule is used to find out the direction of induced current in a conductor.

The phenomenon of producing an induced e.m.f in a conductor or conducting coil due to changing magnetic flux is called electromagnetic induction

Yes, we can produce electricity from magnetism.

A fuse is always connected in series, in household circuits.

A dynamo converts mechanical energy into electrical energy.

A generator with commutator (D.C. generator) produces D.C. current.

An alternating changes its direction after equal intervals of time but direct current does not change its direction.

Frequency of A.C. used in India is 50 Hz.

Frequency of D.C. is zero.

If the current changes direction after equal intervals of time, it is known as alternating current (A.C.).

An alloy of lead and tin is used for making fuse wire.

A.C. is supplied to us in houses.

No, a copper wire cannot be used as a fuse wire as it has low resistance and high melting point.

If the current flows along the same direction with time, it is called a direct current (D.C.).

If a conducting wire is wound in form of a cylindrical coil whose diameter is less in comparison to the length, the coil is called a solenoid.

Switches are always connected in live wire.

Colour code for live wire is red, neutral wire is black and earth wire is green.

The current rating of a fuse is 5 A' means that the maximum safe current permitted to flow through it before it breaks down is 5A.

Yes, kWh is the unit of electrical energy.

The main fuse is connected between the kWh meter and distribution board of the house circuit. The main fuse is connected in the live wire.

It means that if the bulb is lighted on a 200V supply it consumes 60W electrical power or 200J of electrical energy converts into heat and light in 1 second.

The physical quantity is electric power.

Kilowatt-hour is the commercial unit of electricity.

Consumer pays the bill in kilowatt-hour.

Kilowatt-hour is the commercial unit of electricity.

The physical quantity is 'resistance'.

A diagram indicating how various components in an electrical circuit have been connected using symbols for those components is a circuit diagram.

Function of a step-up transformer is to increase the a.c. voltage and decrease the current.

Conductance of a conductor is the reciprocal of resistance of that conductor. Its unit is mho.

The SI unit of specific resistance is ohm-metre (Ωm)

The resistivity of a material is the resistance of a wire of that material of unit length and unit area of cross-section.

The slope of the graph (dV/dI) gives the value of resistance.

An equivalent resistor is that resistor which when replace any combination of resistors the current through the circuit is not altered or changed.

No, Ohm's law does not hold good for semiconductors and electrolytic solutions.

A rheostat is a device used in electric circuit to regulate current without changing the voltage source. It is also called variable resistance.

A key acts as a switch in an electric circuit. It helps to open or close the circuit as required.

A voltmeter has a high resistance.

An ammeter has a low resistance.

The instrument used to measure electric current is called an ammeter. It has a low resistance and is always connected in series.

If the conductor is made thinner, electrons get smaller area of cross-section to flow and it therefore, offers a large resistance.

Charges move in a definite direction in a conductor when a potential difference is applied across the ends of the conductor.