Electric Current And Its Effects

Option (a) – It is correct as a current carrying wire produces a magnetic field. Hence, Option (a) is correct.

Option (b) – Since it has almost zero resistance as it is a conductor, so no heat is produced, so it cannot become red hot (H=i²Rt; H= heat/work done; i is current; R is resistance & t is the time). Hence, Option (b) is incorrect.

Option (c) – As a cell is used to power the bulb which is typical of 2-5V, so it cannot give an electric shock. So, Option (c) is incorrect.

Option (d) – To behave as a fuse, the wire has to burn (to make the circuit open). But, since we have omitted option (b), hence option (d) should also be incorrect.

Option (a) – Yes, it is correct. Every household/buildings have fuses which are now replaced by MCB (Miniature Circuit Breaker) for safety purpose.

Option (b) – Yes, it is also correct. Fuse is designed to limit the maximum current. There is a maximum limit of current above which the fuse blows and the circuit is broken.

Option (c) – This is incorrect. There is only a limit on the maximum current, not on minimum current.

Option (d) – It is correct, the statement is the function of a typical electric fuse.

All the bulbs will glow simultaneously as there is no time lag in the flow of current as soon as the circuit completes.

(i) This statement is ambiguous.

(ii) This is a correct statement as for when a switch is in OFF position the circuit is Open.

(iii) As the circuit is open, so no current flows through it. Hence, it is also correct.

(iv) This is the wrong statement. Current flows immediately or never flow

Option (a) – This statement is correct as a lighted electric bulb is very hot and on touching it can lead to severe burn.

Option (b) – This is also a correct statement as it can lead to a serious mishap.

Option (c) – This is also a correct statement as fuse are made of a particular type of wire.

Option (d) – This is the wrong statement as if we don’t turn the switch to ON position then it is no use to us.

Electric fuse is made from the wires which have a low melting point as when a large current passes through it, it melts quickly and breaks the circuit. This helps in to prevent damage to the electrical appliance. Some material used to make fuse are alloys of zinc, copper, silver & aluminum.

The device used these days in place of the fuse is MCB (Miniature Circuit Breaker). It turns off automatically when large current (larger than the safe limit) is passed through it. Magnetic tripping is the most common principle on which MCB works; it uses magnetic force generated through the current. It has many advantages over traditional fuses

•MCB is more sensitive to current than a fuse.

•In the case of MCB, the faulty zone of the electrical circuit can be easily identified.

•With MCB it is effortless to resume to the supply.

•MCB provides a better interface with the help of knob than a fuse

•Handling MCB is electrically safer than handling a fuse.

•MCB is reusable and hence has less maintenance and replacement cost. Whereas a fuse needs to be replaced whenever it goes faulty.

(i) Conductor.

Our body is a good conductor of electricity as it allows the electric current to pass through it.

(ii) Chemicals

In an electric cell, chemical energy is converted into electrical energy(electricity).

(iii) Safety Device

As a fuse blows off when current large than safety limit is passed through the circuit.

(iv) Battery

A combination of two or more cells, where the positive terminal of one cell is connected to the negative terminal of the next cell, is called a battery.

(i) Battery, it is a combination of two or more cells.

(ii) Fuse, it is safety device in electric circuit.

(iii) Torch, it is a portable lamp powered using battery.

(iv) Switch, an electrical component used to break the circuit.

No, Paheli has not taken a right step as from the excessive heat from the bulb the towel may burn which can lead to a major mishap. Moreover, it is also leading to wastage of electricity.

•CFLs are up to four times more efficient than electric bulbs

•While, initially, they cost more, CFLs are less expensive in the long run because they last much longer than electric bulbs and they use very less electricity.

•They are environment-friendly as they have less carbon emission as compared to the bulb.

Electric fuse is required in all electrical appliances to protect the appliance from getting damaged.

No, we cannot use the same fuse because different appliance like geyser & television set has a different rating and current limit, as well as every fuse, has its rating. So different appliance uses different fuse according to their rating.

(a) Heating effect of current is used in electric heater and geyser.

(b) Magnetic effect of current is used in electric bell and cranes to lift a heavy object.

We cover plug pin holes which are within the reach of children with cello tape or a plastic cover when not in use to prevent children from getting an electric shock. If a child puts his finger in the electric socket, he may get shocked which could be fatal.

Since magnetic effect depends directly on the number of turns of wire on the electromagnet. So, the electromagnet of Paheli will attract more pins as it has number of turns of wire on it and thus it is a stronger magnet.

The following question will come into my mind:

•Why does the iron nail attract the pins?

•What will happen if we increase/decrease the current?

•Does the pin remain attached when we switch off the circuit?

•If we use other material such as wood etc. in place of the iron nail; what change will happen?

(i) No, as we know that resistance is directly proportional to length & H=I²RT where H is the heat/energy; I am current; R is the resistance and T is the time. Since Paheli has a wire which of larger length; hence it will increase more resistance. As current is the same in both the cases, so deciding factor for heat produced is resistance. Hence, Paheli circuit will produce more heat.

(ii) No, as we know that resistance is directly proportional to length and inversely proportional to area. Moreover, H=I²RT where H is the heat/energy; I am the current; R is the resistance and T is the time. Since the wire having more thickness will have less resistance, so less heat will be produced.

From the diagram given below, when the circuit is switched ON, the electric current passed through the coil or solenoid. By the phenomenon of magnetic effect of current, the coil gets magnetized which attracts nearby soft iron armature and the hammer strikes the gong to produce a sound. Thus, the bell starts ringing. When the switch is brought to OFF state, the current flow stops and the magnetisation of coil stop. So, the bell stops ringing.