Questions Related to NCERT

Coils of electric toasters and electric irons are made of an alloy rather than a pure metal due to following reasons:

1. Alloys have higher resistance than pure metals, so they produce more heat when electric current passes through them, which is useful for heating devices.
2. Alloys do not melt easily,  they have higher melting points, so the coils can withstand high temperatures without melting.
3. Alloys are more durable and strong,so the coils last longer under repeated heating and cooling.

If the resistance of an electrical component remains constant and the potential difference across it decreases to half of its original value, then the current flowing through it will also change.

According to Ohm’s Law:
Current (I) = Potential difference (V) ÷ Resistance (R)

Since resistance (R) is constant, if the potential difference (V) becomes half, then the new current will be:
I new = (1/2 × V) ÷ R = (1/2) × (V ÷ R) = (1/2) × I original

This means the current will become half of its original value.

Current will flow more easily through a thick wire than a thin wire of the same material when connected to the same source. 
Because a thick wire has a larger area of cross-section, so it offers less resistance to the flow of current. Lower resistance means more current can flow.

The resistance of a conductor depends on the following factors:

1. Length of the conductor (L): Resistance increases with length.
   (More length → More resistance)
2. Area of cross-section (A): Resistance decreases with a larger area.
   (More thickness → Less resistance)
3. Material of the conductor:  Different materials have different resistivities.
   (Some materials oppose current more than others)
4. Temperature: Resistance increases with temperature (for most conductors).

When we say that the potential difference between two points is 1 volt (1 V), it means that 1 joule of work is done to move 1 coulomb of charge from one point to the other.

In simple words:
1 volt = 1 joule / 1 coulomb

Cell or Battery, These devices supply electrical energy and create the necessary potential difference to allow current to flow through a circuit.

To find the number of electrons in one coulomb of charge:

Charge of one electron = 1.6 × 10⁻¹⁹ coulombs
Number of electrons = 1 ÷ (1.6 × 10⁻¹⁹)
= 6.25 × 10¹⁸ electrons

Hence  6.25 × 10¹⁸ electrons make up one coulomb of charge.

Unit of Current:The SI unit of electric current is the ampere (A).

Definition :-  One ampere is the current when one coulomb of charge flows through a conductor in one second.
So,  1 ampere = 1 coulomb / 1 second

An electric circuit is a closed path through which electric current can flow. It usually includes a power source like a battery, wires to carry the current, and a device like a bulb or fan that uses the electricity.

If the path is complete (closed), electricity flows and the device works. If the path is broken (open), electricity cannot flow and the device does not work.

To find the direction of the magnetic field, we use Fleming’s Left-Hand Rule, which helps determine the direction of force on a current-carrying conductor in a magnetic field.

According to this rule:

• The First finger points in the direction of the magnetic field (B),
• The Second finger points in the direction of current (I),
• The Thumb shows the direction of force or motion (F).

Apply the rule:

• Point your second finger from front to back (direction of current),
• Point your thumb to the right (direction of deflection or force),
• Then your first finger will point upward.

Therefore, the magnetic field is in the upward direction.

The force experienced by a current-carrying conductor placed in a magnetic field is largest when the conductor is placed perpendicular to the magnetic field.

Two methods of producing magnetic fields are:

1. Using a current-carrying conductor– When an electric current flows through a wire, it creates a magnetic field around the wire.
2. Using a permanent magnet – A permanent magnet naturally produces a magnetic field around it without the need for electricity.

The correct answer is:

(c) increases heavily.

The correct answer is:

(d) The field consists of concentric circles centred on the wire

 The properties of magnetic field lines are given below:-

1. Go from north to south outside the magnet.
2. Form closed loops (south to north inside the magnet).
3. Never intersect each other.
4. Closer lines mean a stronger magnetic field.
5. Direction at any point is shown by a compass needle.

A compass needle gets deflected when it is brought near a bar magnet because both the compass needle and the bar magnet are magnets. The compass needle is a small magnet that usually points in the north-south direction due to Earth's magnetic field.

When you bring a bar magnet close to it, the magnetic field of the bar magnet affects the compass needle. The needle gets attracted or repelled depending on the pole of the bar magnet near it. This causes the needle to move or get deflected from its usual direction.

So, the compass needle deflects because of the magnetic force from the bar magnet.

Damage to the ozone layer is a problem because it lets more harmful UV rays from the sun reach the Earth. This can cause skin cancer, eye problems, and harm animals, plants, and crops.

To stop this damage, people are reducing the use of harmful chemicals like CFCs found in old refrigerators and spray cans. International agreements like the Montreal Protocol help control these chemicals. People are also using safer alternatives and spreading awareness about protecting the ozone layer.

If all the waste we make is biodegradable, it will cause less harm to the environment than non-biodegradable waste.

But if a lot of biodegradable waste is dumped in one place and not handled properly, it can smell bad, attract insects, and pollute the soil and water.

So, even biodegradable waste needs to be disposed of carefully to keep the environment clean.

Problems caused by non-biodegradable wastes:

1. Pollution: They cause land, water, and air pollution because they do not break down easily.
2. Harm to animals: Animals may eat plastic or get trapped in it, which can hurt or kill them.
3. Clog drains and cause floods: Plastic and other wastes block drains, leading to waterlogging and floods.
4. Take up space: They pile up in landfills and spoil the beauty of the environment.

Biological magnification means the increase of harmful substances like pesticides in the bodies of living organisms as we move up the food chain.

These substances are not broken down, so they keep getting stored and passed on from one level to the next.

Yes, the levels of magnification are different at different trophic levels. The amount of harmful substances increases at each higher level in the food chain.

Top consumers, like humans, are affected the most.