Electric Current and its Effects Class 7 Worksheet with Answers
Electric Current And Its Effects Class 7 Extra Questions And Answers
In this page we have Worksheet for Class 7 Science Chapter 10: Electric Current and its Effects. We have provided various types of questions for students to practice. Answers to each question is given under the answer tab. First practice the questions on your own and then check the available answers.
Fill in the blanks :
Question 1
(a) The path along which electric current flows is called an______________________
(b) Current does not flow in an___________________________ electric circuit.
(c) Name the alloy used as the heating element in an electric toaster_________________
(d) A fuse wire has a _____________ electric resistance &________________melting point.
(e) ________________________discovered that electric currents create magnetic field.
(f) The credit for the invention of the electric bulbs goes to__________________________
(g) A combination of two or more cells is called a _________.
(h) Full form of MCB is______________________________________________________
(i) Full form of CFL is_______________________________________________________
Answer
(a) electric Circuit
(b) open
(c) Nichrome
(d) High and low
(e) Hans Christian Oersted
(f) Thomas Alva Edison
Question 2
When a switch is in OFF position,
(i) circuit starting from the positive terminal of the cell stops at the switch.
(ii) circuit is open.
(iii) no current flows through it.
(iv) current flows after some time.
Choose the combination of correct answer from the following.
(a) all are correct
(b) (ii) and (iii) are correct
(c) only (iv) is correct
(d) only (i) and (ii) are correct
Question 3
Which of the following precautions need not be taken while using electric gadgets/appliances/circuit?
(a) We should never touch a lighted electric bulb connected to the mains.
(b) We should never experiment with the electric supply from the mains or a generator or an inverter.
(c) We should never use just any wire or strip of metal in place of a fuse.
(d) We should never turn the switch in ON position.
Question 4
Which of the following does NOT contain a heating element?
(a) Electric iron
(b) Electric heater
(c) Electric oven
(d) Electric bell
Question 5
Which of the following statements is correct of a switch?
(a) It allows the flow of electricity.
(b) It controls the brightness of a bulb.
(c) It controls the power of the batteries.
(d) It fuses a bulb.
Question 6
Identify the element that is used for making the filament in bulbs.
(a) Silver
(b) Copper
(c) Aluminium
(d) Tungsten
Answer 2-6
2. (b)
3. (d)
4. (d)
5. (a)
6. (d)
Short answer questions
Question 7
List the factors affecting the amount of heat produced in an element.
Answer
Electric current,
Resistance to heating element and
Time period to utilise the energy.
Question 8
Can we use the same fuse in a geyser and a television set? Explain.
Answer
A geyser heats water. So geyser requires a lot of electricity. Television is used to display pixels. As a result, television uses less electricity than a geyser.
Therefore, for a geyser and a television, we need to use different fuses.
Question 9
What is short-circuiting?
Answer
A short circuit is an electrical circuit that lets a current go in an unplanned direction with no or very little resistance. This causes a excessive electric current to flow through the circuit.
Question 10
Paheli does not have a night lamp in her room. She covered the bulb of her room with a towel at night to get dim light. Has she taken the right step? Give reason to justify your answer.
Answer
Not at all. The Paheli did not do the right thing. The electric bulb wastes energy as heat. So, when she used a towel to cover a bulb in her room at night to get a dim light, it was a complete waste of energy.
Question 11
Give reason why :-
(a) MCB'S are used in place of fuses in homes & offices nowadays.
(b) We should not touch a lighted electric bulb connected to the mains.
Answer
(a) The MCB is more current sensitive than the fuse. It detects any abnormalities in the current flow and shuts down the electrical circuit automatically. Because MCBs are reusable, they require less maintenance and replacement. A fuse, on the other hand, must be changed if it fails.
(b) The lighted bulb attached to the main power source should not be directly touched by our hand, as a lighted bulb can be quite hot and burn our hand as well.
Question 12
Give reason why :-
(a) CFL's are preferred over electric bulbs.
(b) Copper wire used in household circuits does not get hot, but nichrome wire does.
Answer
(a) Compact fluorescent lamps (CFL's) are chosen over incandescent light bulbs because they use less energy and do not waste energy in the form of heat.
(b) Because copper wire has a high melting point, it does not become hot. The melting point of nichrome, on the other hand, is low.
Long answer questions
Question 13
What is an electromagnet? Write Down some practical used of Electromagnets.
Answer
An electromagnet is a type of magnet that generates a magnetic field by using an electric current. An electromagnet is a coil of insulated wire wrapped around a magnetic substance, such as soft iron. As long as current flows through the wire, the magnetic substance acts as a magnet. Motors, generators, electromechanical solenoids, relays, loudspeakers, hard discs, MRI machines, scientific instruments, and magnetic separation equipment all use electromagnets as their components.
Question 14
What is the cause of heating effect of electric current?
Answer
When an electric current flows through a high resistance wire (such as nichrome wire), the wire gets heated. This is known as the heating effect of electric current. Here, electric energy is converted into heat energy when an electric current flows through a high resistance wire.
Question 15
How does the magnetic effect of electric current help in the working of an electric bell? Explain and label the given circuit diagram of an Electric bell. Question 16
Draw the symbols of the following circuit components.
(i) electric cell
(ii) switch in off position
(iii) electric bulb
(iv) battery
