Science 2 Marks Questions

(i) BATTERY
(ii) FUSE
(iii) TORCH
(iv) SWITCH

(i) Heating effect of current is used in electric heater and geyser.
(ii) Magnetic effect of current is used in electric bell and cranes to lift heavy magnetic materials from one place to other.

No, we cannot use same fuse in a geyser and in a television set because the fuse used in every appliances has some limit to withstand the current flows through it.So, different appliances have different fuses.

We do cover plug pinholes which are within the reach of children with cellotape or plastic cover to avoid electric shocks. If unconsciously, a child puts his finger in the electric socket, the shock may be fatal.

(i) What will happen, if we increase the number of coil around the iron nail?
(ii) What is the name of this device ?
(iii) Will it behaves like a permanent magnet ?

(i) The amount of heat produced in a wire depends upon the length of wire, so the amount of heat produced in both the cases will not be equal.
(ii) The amount of heat produced in a wire depends upon the thickness of wire, so the amount of heat produced in both the cases will not be equal.

Yes, electric current have other effects except heating, i.e. magnetic effect of current.
When electric current is passed through a coil, the magnetic field developed around the coil or wire. If magnetic compass is placed near by, it deflects the magnetic needle.

The cell is the unit of battery when more than one cell are combined together, it forms a battery. In trucks, tractors and inverters, cells are internally arranged and we need not to connect it externally, so we called it as batteries.

If cells are placed side by side, then with the help of some connecting wires, the positive terminal of one cell is connected to the negative terminal of other to produce a combined power of all cells which can be called a battery.

No, she has not taken the right step. Because due to excessive heat of bulb, the towel may burn and it also results in the wastage of electrical energy.

Since the magnetic effect directly depends on the number of turns of the coil. As, Paheli's coil has more number of turns than Boojho. So, her electromagnet is stronger than Boojho.
So, electromagnet of Paheli attracts more pins as compared to Boojho.

Advantage: An electromagnet can be turned on or off by controlling the current.
Disadvantage: It needs a continuous supply of electric current to remain magnetized, unlike a bar magnet.

They can be reset after tripping, unlike fuses which need to be replaced.
They react faster and provide better protection against overcurrent and short circuits.

It protects electrical appliances and circuits from damage due to excess current.
It melts and breaks the circuit when the current exceeds a safe limit, preventing fire or damage.

A copper wire cannot be used as a fuse wire because:
Copper has very low resistance and a high melting point.
It will not melt easily when excess current flows, so it cannot protect the circuit from overcurrent.

The three effects of electricity are
(i) Chemical effect
(ii) Heating effect
(iii) Magnetic effect

When the current is passed through the wire bound on the nail, it behave as electromagnet. Due to this reason, the nail attracts the pins.

Electric fuse wire is made up of special material which has low melting point. As if high amount of current is passed, it melts to disconnect the electric circuit and prevent us from causing any damage.

Compact fluorescent lamps are preferred over electric bulbs because electric bulbs use more power of electricity and it also loss electrical energy in the form of heat but it is not so in compact fluorescent lamps.

The lighted bulb connected to main supply should not be touched by our hand directly, as a lighted bulb can be very hot and can burn our hand as well.

The positive terminal is represented by longer vertical line while negative terminal is represented by shorter vertical line.

When an electric current is passed through a coil, it gets magnetised due to phenomena of magnetic effect of current. When magnetic materials such as pins are placed near to it, it gets attracted by the coil or we can say that pins cling to the coil.

Yes, when the current flows through any wire, a magnetic field is developed around that wire or coil and it behaves like a magnet. It can be analysed by placing a magnetic compass around the wire, it will show deflection of the needle.

As we know that, a battery is a combination of two or more cells and it can be constructed by placing cells properly in cell holder in such a way that the positive terminal of one cell is connected to the negative terminal of other.

Electric Bell
An electric bell works on the magnetic effect of current.
Construction of Electric Bell
The electric bell has a U - shaped electromagnet. There is a small iron bar called armature which is held in front of the poles of the electromagnet. The lower end of iron bar is attached to a flat spring and the flat spring is itself fixed to a metal bracket.The upper end of iron bar has a clapper attach to it.A metal gong is fixed near the clapper.

Working of an Electric Bell
• When we pressed the switch of the bell to ring it, an electric current starts flowing in the electromagnet.
• As the electromagnet gets magnetised, it starts attracting the metal spring toward itself.
• As the flat or metal spring moves towards the electromagnet, the clapper which is attached to it strikes the gong and produces a sound.
• When the metal spring is attracted towards the electromagnet, it is no longer in contact with screw and hence circuit breaks.
• When electric circuit breaks, no current flows through the coil, this make the metal spring to go back to its original position and the clapper (hammer) also moves away from the gong.
• This process continues as long as we are pressing the switch.

(i) The electric iron works on the basis of heating effect of electric current.
(ii) The values showed by Pinki here is a great concern and love towards her own 4 years old daughter.

(a) Any of the bulb will not glow when the switch is in the OFF position because circuit is not complete.
(b) All the bulbs will glow simultaneously as the switch is moved to the ON position.

No, we should not agree for replacing a fuse by a piece of wire.
As we know that fuse wire is made up of special material which can be melt on passing high amount of current or during any short circuit. If it is replaced by some other wire, melting of fuse may not take place on short circuiting or excessive current flow and it may cause fire.

No, an electromagnet cannot be used for separating plastic bags from a garbage heap because plastic bags are not magnetic materials. Only magnetic materials can be attracted by the magnet, so plastic bags do not get attracted by the magnet.

Yes, the compass needle shows the deflection, when switch is closed or circuit is complete. On closing the circuit, current flows through the coil and it gets magnetised. Thus, due to this magnetic effect of current, compass needle shows deflection.

When the current is switched ON through a wire or a coil, there is a magnetic field created around the coil or wire and we can say that the wire or coil gets magnetised. Thus, a compass needle kept nearby gets deflected from its north-south position due to other magnet formed by current carrying wire or coil.

The two effects of electric current are
(i) Heating effect
(ii) Magnetic effect

The two cells are connected with the positive terminal in one side. This can be corrected by joining the negative terminal of one cell to the positive terminal of other cell as shown in figure.

To connect all the cells, we should join negative terminal of one cell to positive terminal of other vice-versa.

Complete circuit is shown as below