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1. Electromagnets are not permanent magnets. 

2. Because, they lose the property of magnetism when the circuit is open.

1. Operating a switch with a wet hand. 

2. Removing plug pins when the switch is on. 

3. Using wires without insulation. 

4. Changing bulb when the switch is on. 

5. Holding a person with a current shock.

1. An electric shock occurs when a person comes into contact with an electrical source. 

2. Electricity flows through a portion of the body causing a shock.

1. A cell is made up of three parts, a cathode, an anode and an electrolyte (a chemical). 

2. A cell works by connecting its stored chemical energy, into electrical power 

3. One the electrolyte of the cell is used up it doesn’t work further in non – rechargeable cells (Alkaline cells). 

4. Electrons (negative charges) travel from an anode to a cathode until the anode is considered empty or dead. 

5. A rechargeable cell, a charger can reverse the electron flow again to restore at the anode. This is called charging. 

6. This reversing process depends upon the electrolyte used in the cell. 

7. Normal cells do not contain such type of electrolytes to reverse the charge. 

8. But, the cells like NiMH (Nickel – Metal Hydride), Lithium – ion are capable of reversing the charge when charged it for number of times. 

9. This type of rechargeable batteries are used in rechargeable torch lights, bulbs, mobile phones and fans.

LED Television is one of the most important applications of Light Emitting Diodes. An LED TV is actually an LCD TV (Liquid Crystal Display) with LED display. An LED display uses LEDs for backlight and an array of LEDs act as pixels. LEDs emitting white light are used in monochrome (black and white) TV; Red, Green and Blue (RGB) LEDs are used in colour television.

(i) A ‘Seven Segment Display’ is the display device used to give an output in the form of numbers or text. 

(ii) It is used in digital meters, digital clocks, microwave ovens, etc.

An LED bulb is a semiconductor device that emits visible light when an electric current passes through it. The colour of the emitted light will depend on the type of materials used.

The electric power is the product of the electric current and the potential difference due to which the current passes in a circuit.

The electric potential at a point is defined as the amount of work done in moving a unit positive charge from infinity to that point against the electric force.

(i) Overloading happens when a large number of appliances are connected in series to the same source of electric power. This leads to a flow of excess current in the electric circuit. 

(ii) When the amount of current passing through a wire exceeds the maximum permissible limit, the wires get heated to such an extent that a fire may be caused. This is known as overloading.

1. The earth wire provides a low resistance path to the electric current. 

2. The earth wire sends the current from the body of the appliance to the Earth, whenever a live wire accidentally touches the body of the metallic electric appliance. 

3. Thus, the earth wire serves as a protective conductor, which saves us from electric shocks.

1. When a live wire comes in contact with a neutral wire, it causes a ‘short circuit’. 

2. This happens when the insulation of the wires get damaged due to temperature changes or some external force. 

3. Due to a short circuit, the effective resistance in the circuit becomes very small, which leads to the flow of a large current through the wires. 

4. This results in heating of wires to such an extent that a fire may be caused in the building.

According to Ohm’s law, at a constant temperature, the steady current ‘I’ flowing through a conductor is directly proportional to the potential difference ‘V’ between the two ends of the conductor.

I ∝ V . Hence, = \(\frac{1}{V}\) = constant

The value of this proportionality constant is found to \(\frac{1}{R}\)

Therefore I = (\(\frac{1}{R}\)) v

v = IR

False

According to ohm’s law,

V = IR

Solution : 

Ohm’s law states a relation between potential difference and current.

When 1 joule of work is done in carrying 1 coulomb of charge, from infinity to a point in the electric field, then potential at that point is called 1 volt. Potential difference between two points is 

V = W/Q

or W = Q x v

= 1 x 3 = 3 J

Both the expressions are correct. In the first case where P = I²R current (I) remains constant. Whereas in the second expression where P = V² /R the Voltage (V) remains constant. 

Therefore P = I²R is used where the resistors are connected in series because in the series connection the current in each resistance is constant. 

P = V² /R is used where the resistors are connected in parallel because in the parallel connection the voltage in each resistance is constant. So power becomes inversely proportional to resistance.

1kwh = 1000watt x 3600seconds

= 3.6 x10⁶ wattsecond

= 3.6 x 10⁶ joule (J)

The SI unit of energy is joules (J)

Voltmeter is connected in parallel in the circuit to measure the potential difference between two points.

R = V/I = 220/5 = 44Ω

Number of resisters is = 176/44=4

A voltmeter is always connected parallel to the circuit to measure the potential difference between two points.

Solution :

(i) Equivalent resistance of 10 ohm and 40 ohm resistances (connected in paralel) is R₁, given as 

1/R₁ = 1/10 + 1/40 = 5/40

R₁ = 10 ohm

Equivalent resistance of 30 ohm, 20ohm and 60 ohm resistance (connected in parallel) is R2, given as:

1/R₂ = 1/30 + 1/20 + 1/60 = 6/60

R₂ = 10ohm

R₁ and R₂ are connected in series.

Therefore, Total resistance in the circuit is R = R₁ +R₂ = 8 + 10 = 18 ohm

(ii) Total current flowing in the circuit, I =V/R =12/18 = 0.67 A

Given R₁ = 40 ohms,, R₂ = 60 ohms V = 220 V, t = 30sec

we know that

Total resistance, R = 40 + 60 = 100 ohms

By Ohm's law,

V = IR

I = V/R

 I = 220/100 = 2.2 amp

putting the values of I,R and t in eq. H = I²RT

H = 2.2² x 100 x 30

H = 14520 J

(a) circuit (ii) 

(b) circuit (iii) 

(c) circuit (iii)

Parallel arrangement because if one electrical bulb stops glowing due to some defect the other will keep glowing. Parallel arrangement takes more current from the battery due to its lesser equivalent resistance

1. We can use series connection of cells in torch light, toys, remotes, wall clocks, radio etc. 

2. We can use parallel connection of cells for a long – lasting battery life.

1. Yes, I have observed a large number of bulbs used in decorations of marriage functions, festivals etc. 

2. All the bulbs are connected one after one that means in series.

1. There are two ways to connect more bulbs or cells in an electric circuit they are parallel and series connections. 

2. In parallel connection electricity has more than one path where as in series connection only one path. 

3. If the number of cells are connected in series the brightness of the bulbs enhanced where as in series the brightness of bulb remains same.

1. If we connect two cells and two bulbs in the same path, it is called series connection. 

2. The brightness of the bulbs increased.

a) If more cells are connected in a series, voltage increases in the circuit. That means the strength of the current in the circuit increases. 

b) When we will join lot of cells in a circuit, then the bulb will not be able to handle the large amount of energy supplied to it. Hence, the bulb may damage.

Electricity does not flow through

3. rubber

In a torch, the source of electricity is 

3. the cell 

Correct option is D) does not flow

Correct option is A) Increases

Correct option is B) Decreases

Because if one component fails, the circuit is broken and none of the other components will work. Also components need currents of widely different values to operate properly. But in a series circuit, the current is constant throughout the electric device.

Correct Answer is: (c) θ₁ = θ₂ 

Equal electrostatic forces act on both the bobs. The weights are also the same. Hence, they have identical free-body diagrams.

(a) If both the assertion and the reason are true and the reason is the correct explanation of the assertion.

(i) – (d) 

(ii) – (c) 

(iii) – (b) 

(iv) – (a)