- Electric energy from a cell is used to do work on charges, which is converted into heat in a resistor or other forms, like motion in a motor.
- The work done (energy) in moving a charge Q across a potential difference VAB is:
Work = VAB × Q - Heat produced (H) in a resistor over time t is given by Joule’s Law of Heating:
H = I2 × R × t - According to Ohm’s Law:
VAB = I × R - Electrical power (P) is the rate of energy transfer and is calculated as:
P = VAB × I
Its unit is watt (W), where 1W = 1 volt × 1 ampere.
Definitions [4]
Define fuse.
Electric fuse is a safety device which is used in household wiring and in many appliances.
Define the following:
Electrolyte
The solution through which the electricity passes is called an electrolyte.
Definition: Heating effect of electric current
When a resistor is connected in an electrical circuit, heat is produced in it due to the current. This is known as the heating effect of current.
Define the magnetic effect of electric current.
A current-carrying conductor is always associated with a magnetic field around it is called the magnetic effect of current. It was first discovered by Hans Christian Oersted in 1820.
Formulae [1]
Write the mathematical expression for Joule’s law of heating.
The mathematical expression of Joule’s Law of heating is: H = I2 Rt
Where,
H = Produced Heat
I = Current flowing through the device
t = Time taken
r = Resistance of the appliance
Key Points
Key Points: Electric Circuit
Key Points: Heating Effect of Electric Current
- Heating Effect: Current through a resistor produces heat, calculated by H = I²Rt or H = VIt (Joule’s Law).
- Heat Applications: Used in devices like irons, heaters, bulbs, and fuses (to stop excess current).
- Power Unit: 1 kWh = 3.6 × 10⁶ J, called 1 unit of electrical energy in electricity bills.
- Short Circuit & Fuse: A short circuit causes a large current; the fuse wire melts to break the circuit and prevent fire.
- MCBs: Miniature Circuit Breakers automatically cut off power during overload or fault conditions.
Key Points: Magnetic Effect of Electric Current
- Electric current creates a magnetic field, shown by compass needle deflection.
- Oersted discovered the link between electricity and magnetism in 1820.
- Reversing current changes the direction of the magnetic field.
- Iron filings form circular patterns, showing magnetic field lines around the wire.
- Magnetic field strength increases with current and decreases with distance.
