Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Domestic wiring consists of three types of wires: the Live wire (usually red insulation) at , the Neutral wire (usually black insulation) at , and the Earth wire (usually green insulation) for safety.
The potential difference between the live wire and the neutral wire in India is , and the alternating current (AC) frequency is .
Short Circuit: This occurs when the live wire and neutral wire come into direct contact. The resistance of the circuit becomes almost zero, leading to an extremely high current , which can cause fires.
Overloading: This happens when the total power of appliances connected to a circuit exceeds the capacity of the wires, or when too many appliances are connected to a single socket.
Electric Fuse: A safety device connected in series with the live wire. It consists of a material with a low melting point that melts and breaks the circuit if the current exceeds a specified limit, based on Joule's heating effect .
Earthing: The earth wire is connected to a metal plate deep in the ground. It provides a low-resistance conducting path for the current, ensuring that any leakage of current to the metallic body of an appliance does not give a severe shock to the user.
Parallel Connection: Appliances in a house are connected in parallel so that each appliance receives the same voltage () and can be operated independently with its own switch.
📐Formulae
💡Examples
Problem 1:
An electric oven rated at , is operated in a domestic electric circuit that has a current rating of . What result do you expect? Explain.
Solution:
Given: Power , Voltage . Using the formula , we calculate the current drawn: .
Explanation:
Since the current drawn by the oven () is much higher than the circuit's rated capacity (), the circuit is overloaded. The fuse in the circuit will melt and break the electrical connection to prevent potential fire or damage.
Problem 2:
Why are domestic appliances connected in parallel rather than in series?
Solution:
In a parallel circuit, the voltage across each appliance remains constant at . If one appliance is switched off or fails, the others continue to work.
Explanation:
In a series connection, the total resistance would be very high, reducing the current, and if one appliance fails, the entire circuit breaks. Parallel connection allows independent operation and equal voltage distribution.