Advertisements
Advertisements
Question
What is used to turn off the sudden increase in current in the electrical circuit of the house nowadays?
Advertisements
Solution
Nowadays, Miniature Circuit Breakers (MCB) is used to turn off the sudden increase in current in the electrical circuit of the house.
APPEARS IN
RELATED QUESTIONS
State four most common electrical appliances based on heating effect of electric current. Why do we use finely heated platinum wire in surgery?
An electric iron of resistance 20 Ω takes a current of 5 A. Calculate the heat developed in 30 s.
Why are the conductors of electric heating devices, such as bread-toasters and electric irons, made of an alloy rather than a pure metal?
Name any two effects of electric current.
The safety device based on the heating effect of electric current is called a ______.
Why is a series arrangement not used for connecting domestic electrical appliances in a circuit?
An electric kettle rated at 220 V, 2.2 kW, works for 3 hours. Find the energy consumed and the current drawn.
Why does the connecting cord of an electric heater not glow hot while the heating element does?
Derive the expression for the heat produced due to a current 'I' flowing for a time interval 't' through a resistor 'R' having a potential difference 'V' across its ends. With which name is this relation known?
The current passing through a room heater has been halved. What will happen to the heat produced by it?
The current passing through an electric kettle has been doubled. The heat produced will become:
(a) half
(b) double
(c) four time
(d) one-fourth
Two exactly similar heating resistances are connected (i) in series, and (ii) in parallel, in two different circuits, one by one. If the same current is passed through both the combinations, is more heat obtained per minute when they are connected in series or when they are connected in parallel? Give reason for your answer.
Three heaters each rated 250 W, 100 V are connected in parallel to a 100 V supply. Calculate:
- the total current taken from the supply
- the resistance of each heater and
- the energy supplied in kWh to the three heaters in 5 hours.
Give a scientific reason.
Tungsten metal is used to make a solenoid type coil in an electric bulb.
Identify the figure and give its use.

An electric iron of 1100 W is operated for 2 hrs daily. What will be the electrical consumption expenses for that in the month of April? (The electric company charges Rs 5 per unit of energy).
Statement 1 : Electric current ( flow of electrons ) creates heat in the resistor.
Statement 2 : Heat in the resistor is created according to the rule of energy conservation.
Explain Statement 1 with the help of Statement 2.
Write the mathematical expression for Joule’s law of heating.
The electricity bill specifies the usage in _______.
Live wire and neutral wires have a 220 V potential difference.
When does overloading occur?
True or False – If False give the correct answer
The fuse wire does not melts whenever there is overload in the wiring.
Define fuse.
Mark the correct choice
- Assertion: Electric appliances with a metallic body have three wire connections.
- Reason: Three-pin connections reduce the heating of the connecting wires.
An electric iron consumes energy at the rate of 420 W when heating is at the maximum rate and 180 W when heating is at the minimum rate. The applied voltage is 220 V. What is the current in each case?
Which of the following gases are filled in electric bulbs?
(a) Observe the diagram given below and state whether the bulb will glow or not when we switch on K.

(b) Is it safe to handle the bulb when the switch is OFF?
(c) Give a reason for your answer in (b).
Paheli took a wire of length 10 cm. Boojho took a wire of 5 cm of the same material and thickness. Both of them connected the wires as shown in the circuit given in the following figure. The current flowing in both the circuits is the same.
- Will the heat produced in both cases be equal? Explain.
- Will the heat produced be the same if the wires taken by them are of equal lengths but of different thickness? Explain.

Copper wire offers very little ______ and does not get heated up quickly.
A student boils water in an electric kettle for 20 minutes. Using the same mains supply he wants to reduce the boiling time of water. To do so should he increase or decrease the length of the heating element? Justify your answer.
What is a trip switch?
An electric fuse is a wire made up of a material having ______ melting point.
A fuse is used in an electric circuit to stop high currents flowing through the circuit.
The electric fuse works on the Joule heating principle.
Find the odd one out.
In the electric equipment producing heat like iron, electric heater, boiler, toaster etc., an alloy such as nichrome is used, not pure metals.
In a set up the students coated iron nails with zinc metal and noted that, iron nails coated with zinc prevents rusting. They also observed that zinc initially acts as a physical barrier, but an extra advantage of using zinc is that it continues to prevent rusting even if the layer of zinc is damaged. Name this process of rust prevention and give any two other methods to prevent rusting.
An electric kettle consumes 1 kW of electric power when operated at 220 V. A fuse wire of what rating must be used for it?
State the law that explains the heating effect of current with respect to the measurable properties in an electrical circuit.
When a current I flows through a wire of resistance R for time t then the electrical energy produced is given by ______.
