Published by: Nuru
Published date: 06 Jul 2021
Electricity and magnetism are two related phenomena produced by electromagnetic force. Together, they form electromagnetism. A moving electric charge generates a magnetic field. A magnetic field induces electric charge movement, producing an electric current.
An electrical circuit is a path in which electrons from a voltage or current source flow. The part of an electrical circuit that is between the electrons starting point and the point where they return to the source is called an electrical circuit's "load".
An open circuit is one where the continuity has been broken by an interruption in the path for current to flow. A closed-circuit is one that is complete, with good continuity throughout. A device designed to open or close a circuit under controlled conditions is called a switch.
The combination of cells is the arrangement of the cells that is designed to get the maximum potential difference and the current supply is called a combination of cells.
In this combination, the positive terminal of one cell is connected to the negative terminal of the other cell.
Total potential in this case (V) = sum of the individual p.d of the cell.
The current in the external resistance is the number of times the current due to t e single cell
The cells are said to be parallel if the positive terminal of all cells is connected at one common point and the negative terminal is connected to one common point.
In a parallel combination of cells the total voltage between any two points is always constant this is equal to the voltage of one cell.
When the resistors are connected end to end then it is called the series combination of the resistor.
If R1 R2 R3 are connected as shown in the figure then
R= R1 + R2 + R3 and if V1 V2 V3 is the voltage across resistors respectively.
V= V1 + V2 + V3
The value of the current is the same in each resistor but the p. d is different. If one of the resistors does not work then it affects the whole combination.
When the resistors in the circuit are connected between the two common points, then the combination is called a parallel combination. The voltage in each branch is the same.
In this case total current (I) = I1 + I2 + I3 …………………..1
From the ohm law
I1 = V/R1
I2 =V/R2
I3 =V/R3
Putting the value in 1
V/R = V/R1 + V/R2 + V/R3
1/R = 1/R1 + 1/R2 + 1/R3
We get, the reciprocal of effective resistance in parallel combination is equal to the sum of the reciprocal of each resistance.
The electric power of the device is defined as the rate at which electrical energy is converted into another form of energy.
The electrical power of the device is the product of the current (I) and voltage (V) across.
P = VI
P = V*V/R from ohm’s law V = IR
P = V2/R
P =RI2
Fuse is a safety device to protect a circuit from excessive heating. A fuse wire is a short metal wire having low melting point made of an alloy of tin and lead. It is connected in series with a circuit.
The overflow of the current due to the low reactance path in the circuit is called short-circuiting.
A transformer is a device that is used to convert low ac voltage into the high a.c voltage or vice –versa.
A step-up transformer is used to convert low a-c voltage to high ac voltage
A step–down transformer is used to convert high a-c voltage to low ac voltage
When an alternating emf is applied to the primary coil, a changing current flowing in it produces an alternating magnetic flux in it. This causes to change in the magnetic flux linked with the secondary coil. An alternating emf is then induced in the secondary coil. It is called the principle of mutual inductance on which transformers are based.
Uses: Transformers are used in computers, television, air-condition, doorbells, etc.
Electrolysis of water is the decomposition of water into oxygen and hydrogen gas due to the passage of an electric current. It is also called water splitting. It ideally requires a potential difference of 1.23 volts to split water.
When dil. H2SO4 is mixed with water
H2O(HOH) H++ OH-
At anode
OH-- OH + e-
4O 2H2O + O2
At cathode
H+ + e- H
4H 2H2
Electroplating involves passing an electric current through a solution called an electrolyte. This is done by dipping two terminals called electrodes into the electrolyte and connecting them into a circuit with a battery or other power supply.
Here CUSO4 solution is taken as the electrolyte. When the electric current passes through the circuit, a thin layer of copper is deposited over the metal.
Chemical reaction involved
‘When cuso4 dissolves in water
CuSO4 → Cu++ + SO4
At anode: Cu + SO4 → CuSO4 + 2e
At cathode: Cu++ +2e → Cu
Application of electrolysis
The lighting effect of current:
Some electrical devices convert electrical energy into light energy this is called the lighting effect of electric current
The lighting effect of current is used in:
Fluorescent lamp:
A fluorescent lamp consists glass tube filled the mercury vapor and coated with fluorescent powder. It converts 30% of the electrical energy to light energy and very useful for household purposes.
Filament lamp:
A filament lamp has tungsten filament with inert gases filled inside the bulb. These inert gases prevent the oxidation and evaporation of tungsten metal at high temperatures. It converts 10% of the electrical energy into light energy.
Fleming’s right-hand rule states that “If the first three fingers of the right hand are held mutually perpendicular to each other, with the index finger in the direction of the magnetic flux and the thumb in the direction of motion of coil, the middle finger points to the direction of the induced current.”
Fleming’s right-hand rule is used to determine the direction of the induced current in a generator.
Ac and Dc circuit: In direct current (DC), the electric charge (current) only flows in one direction. Electric charge in alternating current (AC), on the other hand, changes direction periodically. The voltage in AC circuits also periodically reverses because of the current changes direction.
Graph of ac and dc circuit
Electromagnetic induction
The phenomenon of inducing the emf in a closed circuit whenever there is a change in the magnetic flux is called electromagnetic induction. The resulting current is called an induced current.
Faraday's laws of electromagnetic induction are:
1. Whenever magnetic flux linked with a closed circuit changes, an emf is induced in the circuit.
2. The induced emf lasts as long as the change in the magnetic flux is taking place.
3. The magnitude of the induced emf is directly proportional to the rate of change of the magnetic flux.
