Science [2 Mark Questions]

In electric heater we use wire which have high resistance light is nichrome wire because they here we want to heat and the wire high resistance will produce high heat. And in fuse wire
we use the wire which have very low resistance such as copper wire because here we want to less electric current and less resistance because if it heat then it will break down because
when short circuiting hokka then it will break easily in less electric current.

Energy used by a TV set of power 250 W in 1 hour = P × t = 250 Wh.
Energy used by toaster of power 1200 W in 10 minute (10/60 h)
= P × t = 1200 W × 10/60 h = 200 Wh.
Therefore, TV set will use more energy.

Given: V = 230V, I = 0.4 amp
Rate at which electric energy is transformed = Power
Power = V × I
= 230 × 0.4
= 92W = 92J/s

The electrical fuse is a safety device against overloading and short circuiting of any electrical circuit. A fuse is placed in series with the circuit so that the same current flows through the
fuse and the electrical circuit. The rating of a fuse indicates the maximum current which can flow through a fuse without blowing it off. If a fuse of higher rating is used, then it will not
blow off even when the current exceeds the safety limit of the appliance. As a result, the electrical appliances may get damaged.

It is given that resistance R of the electrical component remains constant but the potential difference across the ends of the component decreases to half of its value. Hence, as per Ohm’s law, new current also decreases to half of its original value.

I = 6 amp, R = 40 ohm
We know that
V=IR
V = 6 × 40 = 240V.

One watt hour is the amount of electrical energy consumed when an electrical appliance of 1 watt power is used for 1 hour.
1 watt hour = 3600 joules.

Parallel circuits – Because if one electrical appliance stops working due to some defect, then all other appliances in the circuit will keep working properly.

Both the bulbs are connected in parallel. Therefore, potential difference across each of them will be 220 V, because no division of voltage occurs in a parallel circuit. Current drawn by the bulb of rating 100 W is given by, Power = Voltage × Current
Current = Power/Voltage = 60/220A
Hence, current drawn from the line = 100/220 + 60/220 = 0.727 A

An electric fuse is a safety device used to protect circuits and appliances by stopping the flow of any unduly high electric current. It works on the principle of the heating effect of electric current.
It is made up of material having low melting point and connected in series with the circuit. When current passing through the fuse exceeds a certain limit then it melts. Due to which the circuit breaks and current stops flowing.

Conventional direction of flow of electric current is from positive terminal of a battery to the negative terminal, through the outer circuit. The direction of flow of electrons is opposite to the direction of conventional current, i.e. from negative terminal to positive terminal.

1. By increasing the area of cross section, the resistance will decrease.
2. By increasing the diameter, the resistance will decrease.

T​he V - I graph (at constant temperature) for a conductor following the Ohm’s law is a straight line with a positive slope.

The slope of the graph with current on the vertical axis and potential difference on the horizontal axis represents the Resistance of the material of the conductor.

The electric potential (or potential) at a point in an electric field is defined as the work done in moving a unit positive charge from infinity to that point.Unit of electric potential is volt.

I = 5amp, V = 220 Volt, t = 2h
P = ?, E = ?
P = V × I
= 220 × 5
= 1100 watt
= 1.1KW
Energy consumed, E = P × t
= 1.1 × 2
= 2.2KWh

Electric current is the flow of electric charges (electrons) in a conductor such as a metal wire.
SI unit of electric current is ampere.

The statement is correct if the weather is very dry and wire is not carrying very high voltage. Because dry air is very bad conductor of electricity and hence current will not flow through your body, since circuit is incomplete. But if humidity is high then current can leak through air from your body, so it will be bad idea to do it in rainy season. Also if the wire carrying very high voltage, then there is also a possibility that the air can break down you may be electrocuted.

Mixed combination of resistance means when two or more than two resistors are connected in series and parralel simultaneously. Resistor circuits that combines series and parallel resistors networks together are generally known as resistor combination or mixed resistor circuits. These type of combination are known as Mixed combination.

1. A long piece of nichrome wire.
2. A thin piece of nichrome wire.

When an electrical appliance consumes electrical energy at the rate of 1 joule per second, its power is said to be 1 watt.
1 watt = 1 volt × 1 ampere.

According to the law of combination of resistances in series, the combined resistance of any number of resistances connected in series is equal to the sum of the individual resistances.

A voltmeter is connected in parallel across any two points in a circuit to measure the potential difference between them with its +ve terminal to the point at higher potential and -ve terminal to the point at lower potential of the source.

The rate at which electrical work is done or the rate at which electrical energy is consumed is known as electrical power.
It is given by P = VI = Watt
P = VI = Watt

Given: V = 3V, I = 0.5 amp

1. R = ?

we know that V = IR

3 = 0.5R

R = 6 ohms

2. Power of lamps = VI

3 × 0.5

= 1.5 watt