Advertisements
Advertisements
Question
My mother was operating washing machine on Sunday morning. Suddenly, she saw a spark coming out of the electric board and the electric current in the house failed. An electrician was called to look into the matter. What should he have noticed.
Solution
- When electrician was called, he checked circuit and found that circuit catches fire due to short circuit.
- He observed that live wire and neutral wire came in direct contact which resulted in short circuit.
- Because short circuit resistance of the circuit becomes very small and hence huge amount of current flows through it.
- It ultimately produces a large amount of heat and raises the temperature. As a result circuit catches fire.
APPEARS IN
RELATED QUESTIONS
Calculate the number of electrons constituting one coulomb of charge.
In 10 s, charge of 25 C leaves a battery, and 200 J of energy are delivered to an outside circuit a result.
What current flows from the battery?
Which unit could be used to measure current?
(a) Watt
(b) Coulomb
(c) Volt
(d) Ampere
Christmas tree lamps are usually wired in series. What happens if one lamps breaks?
Draw a circuit diagram showing two lamps, one cell and a switch connected in series.
How can you change the brightness of the lamp?
Consider the circuit given below when A, B and C are three identical light bulbs of constant resistance. 
(a) List the bulbs in order of increasing brightness.
(b) If C burns out, what will be the brightness of A now compared with before?
(c) If B burns out instead, what will be the brightness of A and C compared with before?
For a heater rated at 4 kW and 220 V, calculate:
(a) the current,
(b) the resistance of the heater,
(c) the energy consumed in 2 hours, and
(d) the cost if 1 kWh is priced at Rs 4.60.
A switch must be connected in:
(a) Live wire (b) neutral wire
(c) earth wire (d) either earth or neutral wire
An electric current flowing in a wire creates __________ around the wire.
What is international convention of colour coding in a cable?
Tick(✓) the correct choice in the following:
A three pin plug is connected to the lead for a 1 kW electric iron to be
used on a 250 V supply. Which of the following statements is not correct?
Find the effective resistance in the following circuit diagrams (Fig.):
Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. The resistance of each heater
A battery of e.m.f. 15 V and internal resistance 2 Ω is connected to two resistors of resistances 4 ohm and 6 ohm joined (a) in series. Find in each case the electrical energy spent per minute in 6 Ω resistor.
Match the items in column-I to the items in column-II:
| Column - I | Column - II | ||
| (i) | electric current | (a) | volt |
| (ii) | potential difference | (b) | ohm meter |
| (iii) | specific resistance | (c) | watt |
| (iv) | electrical power | (d) | joule |
| (v) | electrical energy | (e) | ampere |
A charge of 400C flows through a conductor for 13 minutes and 20 seconds. Find the magnitude of the current flowing through the conductor.
Define the following:
Conventional current and electron current
