Electricity And Circuits

In an electric circuit, there is a cell which has two terminals, positive and negative. The current leaves from the positive terminal and enters from the negative terminal to complete the electric circuit. A positive terminal on a cell is shown by a (+) sign or the side where you will observe a small cap like outing cover. So, in the figure, you can observe that only in Fig. B the current leaves from positive terminal and enter back in the negative terminal. But in another figure this is not shown hence B is the correct answer.

The statement (a) say that the switch is the source of electric current in the electric circuit but we know that the source of electricity in an electric circuit is an electric cell. An electric cell provides current in the source, while switch only helps to complete or break the circuit.

According to Statement (b), the switch helps to complete or break the circuit which is true because it breaks the circuit when it is on "OFF" mode but it completes the circuit when it is on "ON" mode.

Statement (c): When we "OFF" the switch the circuit breaks and the bulb goes off but when we "ON" the switch the circuit completes and the bulb glows, hence the switch help us to use the electricity as per our requirement. So statement (c) is true.

Statement (d) says that when the switch is open or "OFF" the circuit breaks and the bulb goes off. Which happen because there is an air gap between its terminal and hence the statement (d) is also true.

Option A: The glass case of the bulb does not glow at all. The glass case is to keep all the gases inside and to protect the filament and inner wires of the bulb. So, option (a) is not the correct option.

Option B: The thin filament actually glows up when we switch on the electric circuit. This happens as when we "ON" the switch the electric current flows through the circuit and the flow of current increase the temperature of the filament resulting in the glowing of the filament. It is like when you heat an iron bar too much it turns into a red glowing iron bar.

Option C: The thick wires do not glow in the bulb, they are just for supporting filament and passing the current to it.

Option D: Gases do not glow

Steel spoon, metal clip, and copper wire all or made of metal while the plastic clip is a non-metal thing. And we know that only metals conduct electricity that's why they are conductors and non-metals do not conduct electricity that is why they are insulators. Hence, conductors allow the current to flow that is why option (a),(b) and (d) are not right option and only (c) is the correct option which does not allow current to flow and will not let the bulb glow.

The key difference between conductors and insulator is that conductor conduct electricity while insulators do not.

To answer this type of question we have to fully understand the concept as well as the question. The question here wants to ask which bulb will glow first. The key concept here is that for a bulb to glow the circuit must be complete. Only when the bulb will glow. Option (a) states that bulb A will glow but the bulb A will not glow until the circuit completes. And if the circuit completes, all bulb will glow together because all are connected to each other. The circuit process in following steps:

● Current leaves from the positive terminal.

● Current enters the bulb A, but the circuit is not complete, hence bulb does not glow.

● Current enters the bulb B, but the circuit is not complete, hence bulb does not glow.

● Current enters the bulb C, but the circuit is still not complete hence bulb does not glow.

● But when the current enters the negative terminal the circuit completes and all the bulb will glow at once.

The simple logic here is that all bulb will help to complete the circuit, that is why the current will flow through them at the same time and hence they will glow together.

The filamentis the actual part in the bulb which glows. A bulb works on the basis that when current is supplied to the filament it heat ups and this heating of the filament will make the filament glow like a glowing iron bar; that is for example when you heat an iron bar too much it turns into a red glowing iron bar.

So, the main working of the bulb is to supply the current to the filament it will get heat up and start glowing. Whereas the two thick wires are for supporting that filament into its place and the metal case has both terminals on it.

Glass bangle, thick thread and rubber pipe metal all are non-metal while steel spoon is a metal thing. And we know that only metals conduct electricity that's why they are conductors and non-metals do not conduct electricity that is why they are insulators. Glass, thread and rubber are insulators and steel spoon is a conductor. Hence, insulators does not allow the current to flow that is why option (a),(b) and (c) are not right option and only (d) is the correct option which does allow current to flow and will let the bulb glow.

The key difference between conductors and insulator is that conductor conduct electricity while insulators do not.

The (C) is the correct option.

In figure (A) there is no bulb, the circuit is complete but it just connect the negative and positive terminal of the cell. And cell is the source of electricity but in this case we are not using electricity instead current is just flowing through the circuit not using up.

In figure (B), there is a bulb and the circuit is also complete hence the bulb will glow and will use the electricity and the cell will be used up; but in figure (C) there are 2 bulb hence consuming electricity at a much faster rate than figure (B) and (A) resulting in a higher rate of consumption of cell and as a result the cell will be used up

Number 3 and 4 label the terminals of the bulb.

Terminals are those part through which the electricity is passed to the filament of the bulb. They are made up of metal because their work is to conduct electricity to the filament. Terminals are like gates, if you want to go inside the room there is only one way that is passing through the gate. In case of bulb, if you want to enter the current into the filament you must pass it through the terminals. Without passing through terminals there is no other way.

Steps to show the connections to make the bulb glow:-

● There are two terminals of an electric cell. Connect the positive terminal of the electric cell to one terminal of the switch by the given connecting wires. Current starts from the positive terminal and passes through the switch.

● Now, connect the second terminal of the switch to the one terminal of the bulb by connecting wires. The current passes through the switch and bulb but still the circuit is not complete, so the bulb will not glow.

● The last step is to connect the other terminal of the bulb to the negative terminal of the cell. This completes the electric circuit, as current starts from positive terminal goes to switch, if switch is close it goes to bulb and then it completes the circuit by going to the negative terminal. This make the complete electric circuit.

The bulb will not glow.

In this circuit, switch is open that is circuit is broken, so the bulb will not glow. Switch helps to complete or break the circuit as it breaks the circuit when it is on "OFF" mode but it completes the circuit when it is on "ON" mode, hence the switch help us to use the electricity use as per our requirement. Which happen because as there is an air gap between its terminal when it is open or on "OFF' mode.

The two possible reason behind that are:

● The first possible reason is that may be the filament inside the bulb is broken. Filament is the main component of the bulb which glows when the current passes through it. It glows because when electricity passes through the filament it got heat up. Heating causes the glowing of bulb. But the extensive heating can break the filament and will result in not glowing of the bulb.

● The second possible reason is that the electric cell is completely used up or all the chemicals have been used already and there is no electricity left in it. As cell is the only source of the power of the circuit, if it is completely used the circuit will not work and the bulb will not glow.

The diagram shown below is correct arrangement to join three electric cell inside the torch so that the bulb glows,

The current start from the positive terminal of the cell and will come up back into the negative terminal of the cell.

If a bulb require three electric cell the most important thing is how you arrange the cell. The correct arrangement is that when positive terminal of one cell is attached to the negative terminal of the another.

Now, it will work like current from one cell will leave and will enter into another cell {from negative terminal of the second cell} there it will add with the current of second cell and they both will leave {from positive terminal of the second cell} and then they will enter into third cell{ through the negative terminal of the third cell} after that all the current sum up and will go into the circuit from the positive terminal of the third cell.

The key point here is Current can leaves from positive terminal of the cell only and enter into cell from negative terminal, we have to fulfill these two condition to make this arrangement.

Rechargeable batteries are those batteries which are reusable after they are discharged by recharging them.

The main principle of battery is that the chemicals inside the battery react and produce electricity, but once those chemical reacts completely there is no electricity left, then the battery is said to be a discharged battery.

But, there is a way to use discharged batteries again by reversing the reaction which produce electricity. That is, if we reverse the reaction which uses all the chemicals inside the battery and produce electricity, the chemical will again start generating electricity. This is the working of rechargeable battery.

The reaction which consume all the chemicals and produce electricity inside the cell is reversed and this is done by charging of the battery. That is how rechargeable batteries work.

The bulb A will not glow.

As we know, if a circuit is not complete the bulb will not glow. The filament is the glowing part of the bulb as well as it is the connecting part. It completes the circuit within the bulb.

If the filament of the bulb B is broken the circuit is not complete and hence bulb A will not glow. If any of the component is broken which completes the circuit the circuit will not work. The most important condition is to first complete the circuit.

If any other bulb is also connected it will also not work. Because there is no complete way for a current.

A bulb has two terminals, one for sending the current to the filament and other is for receiving it back. Every electric component has two terminal one to send the current to device one to receive it back. It is not possible for any device to have only one terminal.

Also two terminal have important role in completion of the circuit. That is the most important condition for working of the circuit is that it must be complete it must not have any break point. Due to the concept of two terminal the circuit is always complete.

It is like a human chain as human have two hands one hand to connect with one person and other hand to connect other. At the end of the chain the first person and the last person join their hand. The person here are symbol of electric appliances, which have two hand as two terminal. If the electrical appliances are connected to each other like human chain than only circuit works.

(A) is the inappropriate setup.

In figure B the electric cell is connected to two bulbs and both bulb will consume the cell at very high rate but we are getting more light if we connect two bulb.

In figure C the cell is connected to a bulb which will consume less electricity than the two bulb and it will also give us light.

In figure D the cell is connected to a bulb using a switch which is the most appropriate way to connect bulb, it will use the electric cell at very low rate.

In all these cases we have seen that if cell is getting used up we are getting output in form of light. There is no wastage of energy in these three cases, but in the figure A, positive terminal of the cell are connected to negative terminal of the cell. We are not using current it is just flowing through the wire. And after some time the whole chemical will get consumed up and we will get nothing in return, hence that is why figure A is wrong.

A fused bulb is a bulb whose filament is broken. The filament is the main glowing part if it is broken the bulb will obviously not glow. Because the circuit will be broken.

A bulb works on the basis that when current is supplied to the filament it heat ups and this heating of the filament will make the filament glow like a glowing iron bar; that is for example when you heat a iron bar too much it turns into a red glowing iron bar.

So, the main working of the bulb is to supply the current to the filament it will get heat up and start glowing. But when the current increases too much, the temperature of the filament also increases highly. This increase in the temperature of the filament can break or melt the filament which results in breaking of the circuit. And this broken filament bulb is called fused bulb. And that is why fused bulb does not glow.

If Paheli connects the positive terminal of the cell to one terminal of the bulb with aluminum strip and negative terminal of the cell to other terminal of the bulb with the second aluminum strip, then the torch bulb will glow. Then she will succeed.

Aluminum strips are metal strips and metals are classified as conductors. That is conductor are those substance through which electricity can pass or they can conduct electricity. The aluminum strips will work as connecting wires and will complete the circuit. And that is how the light bulb will glow.

Our problem here is that,

we have to connect the bulb using only one wire. The way to do so is to connect one terminal of the bulb directly to the negative terminal of the electric cell by doing so we will no longer require any other wire for our electric circuit.

In the picture as you have observed the negative terminal of the cell is directly connected to the bulb without any wire.

(i) We know that direction of current flow is always from positive terminal of battery to negative terminal through the whole circuit. So,

● in first case, the direction of current flow is from Q to P

● in second case it is from P to Q.

(ii) Yes the bulb will glow in both cases as there is flow of current through circuit in both the cases.

(iii) No, the brightness of glowing bulb does not depend on direction of current flow. It just depends on amount of current and voltage through it.

Some of the possible reasons are:

● The cells may have been used up.

● Cells might not have been arranged in correct order.

● The bulb may have been fused.

● The switch might be faulty.

(Write any three).