Effects of Electric Current

Law of Conservation of Energy

Read the paragraph below and fill in the missing words.

Energy can neither be nor . It can only be converted from one form to another

Enable JavaScript

Energy Changes and their Usages

Read and complete
Mixie To grid Electrical to Energy
Electric bulb To get Light to Light Energy
Induction cooker To get heat Electrical to Energy
Storage battery (while charging) To store energy Electrical to Energy
Storage battery (while ) To get energy Chemical to Electrical Energy
To get energy Light to Electrical Energy

Enable JavaScript

Electric Charge and Current

Analyse the circuit  and fill in the missing words.

Ammeter is a device used to measure through the circuit and it is connected in with the resistor.

Voltage across the resistor is measured using Voltmeter which connects in to the resistor.

Electric current is the electric charge flows through the circuit in time.

Electric current I = Charge / time

That is charge flows through the conductor in t second , Q = I t Coulomb

Enable JavaScript

Potential Difference

Question 1

Work done to move 1 C of charge through 1 V potential difference is 1 joule

Question 2

2 joules of work is required to move 2 C of charge through unit potential difference

Question 3

Power consumed in the circuit is V I and the energy expended by the battery is V I t

Joule's Law

The heat generated (H) in a current carrying conductor is directly proportional to the product of the square of the current (I) in the conductor, the resistance of the conductor (R) and the time (t) of flow of current.
                              H ∝ I2Rt

Fill the blanks with (H,2H,4H,H/2,H/4)

Resistance of conductor R (Ω) Intensity of Current I (A) Time for which current flows t (s) Change in Heat (H)
2R I t
R 2I t
R/2 I t
R I/2 t
R I 2t
R I t/2

Enable JavaScript

Arrangement of Resistors in Circuits

When a circuit is completed by connecting the resistors one after the other, it is called series connection

A parallel circuit is a closed circuit in which the current divides into two or more paths before recombining to complete the circuit.

Select the answers in the following table(Resistors have different values)

Mode of connection of resistances Effective Resistance Voltage obtained in each resistance Current through each resistance
Series Connection
Parallel Connection

Enable JavaScript

Colour Code

Color Code

Select color codes

Resistance First color Second color Third Color Tolerance
27 kΩ ± 10% Violet Orange
5.6 kΩ ± 5% Green Gold
890 Ω ± 20% White No ring

Enable JavaScript

Select the currect answer

Question

If n resistors of the same value (r) connected in series , then effective resistance R =

Hint

Effective resistance increases in series connection

Answers

rn

nr

r/n

n/r

Feedback

Question

If n resistors of the same value (r) connected in parallel , then effective resistance R =

Hint

Effective resistance decreases in parallel connection

Answers

rn

nr

n/r

r/n

Feedback

Heating Effect of Electricity

Heating coils are made of nichrome. Nichrome is an alloy of nickel, chromium and iron

An ideal heating coil must have resistivity, melting point and ductility. It has an ability to remain in red hot condition for a long time without getting

Enable JavaScript

Safety fuse

Question

Choose the correct statement about Safety fuse

Answers

Alloy of tin and lead can be a fuse wire

It is an alloy of nickel and chromium

Fuse wire has a relatively low melting point

It should be connected in parallel with the circuit

Feedback

Appliances without heating coil

Microwave oven and induction cooker are appliances which do not use a heating coil

Question 1

In a microwave oven, microwaves are used and induction cooker uses eddy currents.

Electric power

An electrical appliance works by making use of electrical energy. Hence it has a power.

Power is the work done per unit time.

Power equation

The amount of energy consumed by an electrical appliance in is its power.

Enable JavaScript

Incandescent lamps

Question

Tungsten can become white hot and emit white light for a long time. So it is used as filament in Incandescent lamps. Select the true statement about tungsten.

Answers

It has low resistivity

It has low melting point

It has low ductility

Ability to emit white light in the white hot condition

Feedback

Nitrogen

Question

Why is Nitrogen filled in filament lamps? Select the true statements about nitrogen

Answers

At normal temperature and pressure, nitrogen behaves like an inert gas.

Small increase in temperature does not influence the expansion of nitrogen.

Vaporisation can be reduced by filling some nitrogen at low pressure inside the bulb.

Feedback

Problem with heat

A major part of the electrical energy supplied to an incandescent lamp is lost as heat.

Hence the of these devices is less.

Enable JavaScript

Discharge lamp

Discharge lamps are glass tubes fitted with two electrodes. They emit light as a result of discharge of electricity through the gases filled in tubes.

When a high potential difference is applied the gas molecules get .

Visible rays are emitted from these molecules or atoms when they attain the state for the sake of .

Enable JavaScript

Colors emitted from the Discharge tube

Depending on the difference in the energy levels lights of different colours and other radiations are emitted. The colour depends on the nature of the gas filled in the lamp

Gas Colour
Hydrogen
Chlorine
Nitrogen
Neon
Sodium Vapour

Enable JavaScript

LED bulb (Light emitting diode bulb)

LED bulbs are more efficient than other bulbs. Low power consumption, high efficiency and high longevity are the advantages.

  • As there is no , there is no loss of energy in the form of .
  • Since there is no in it, it is not harmful to environment

Enable JavaScript

Important units

Read and complete

Work has same unit of Energy, and it is . It is the SI unit.

Another unit of energy is calorie. One calorie = joules.

Power is the rate of doing work and its unit is .

Unit of electric charge is .

Current is the charge per unit time and its unit is ampere or .

Potential difference has its unit as .

Unit of resistance is

Enable JavaScript

Licensed under the Creative Commons Attribution Share Alike License 4.0