8 Sci – 4 Electricity Magnetic and Heating Effects – Complete Chapter – (FREE MCQ Test)
1 / 25
By changing which property of the electric circuit can the poles (North and South) of an electromagnet be reversed?
The poles of an electromagnet can be reversed by changing the direction of the current flowing through the coil.
2 / 25
In a simple lemon cell constructed in Activity 4.6, what acts as the electrolyte?
When making a lemon cell using copper wires/strips and iron nails, the lemon juice acts as the electrolyte, helping to conduct electricity.
3 / 25
What is a Voltaic cell (also known as a Galvanic cell) defined as?
A Voltaic cell is a device that generates electric current due to chemical reactions taking place inside it, consisting of two metal plates (electrodes) and an electrolyte.
4 / 25
What phenomenon occurs when electric current flows through a conductor and produces a magnetic field around it?
When electric current flows through a conductor (like a wire), it produces a magnetic field around it. This is known as the magnetic effect of electric current.
5 / 25
Which of the following common devices works primarily based on the magnetic effect of electric current?
The magnetic effect of electric current has many practical applications, such as in devices like electromagnets, electric bells, motors, fans, loudspeakers, and more.
6 / 25
In the presence of a current-carrying wire, why does a magnetic compass needle deflect?
The deflection indicates that the current-carrying wire has a magnetic effect on the compass needle, meaning a magnetic field is present around the wire.
7 / 25
The amount of heat generated in a wire due to current flow depends on the material, thickness, length, and the duration for which the current flows. What is the other crucial factor mentioned that affects the heat generated?
The heat generated depends on the magnitude of the electric current (which increases when using more cells/batteries).
8 / 25
In household circuits, why are safety devices placed in the circuit?
Safety devices are placed in household circuits to minimize incidents caused by overheating in appliances, which can lead to damage to plugs/sockets or even fires.
9 / 25
Which of the following household appliances works based on the principle of the heating effect of electric current?
Household appliances like electric room heaters, stoves, irons, immersion rods, water heaters, kettles, and hair dryers work on the principle of the heating effect of electric current.
10 / 25
Which of the following factors, if increased, would lead to a stronger electromagnet?
The strength of an electromagnet can be changed by changing the amount of electric current flowing through the coil or the number of turns of the coil, or both.
11 / 25
Why does a conductor get heated when electric current flows through it?
When electric current flows through a conductor, it faces some opposition or resistance to its flow, causing some of the electrical energy to be converted into heat energy.
12 / 25
Which specific type of wire is commonly used for heating elements in household appliances because it offers higher resistance compared to copper wire of the same size and length?
A nichrome wire, for example, offers higher resistance compared to a copper wire of the same size and length, leading to significant heat generation.
13 / 25
Why is a dry cell called ‘dry’?
Dry cells are called ‘dry’ because the electrolyte is not a liquid but a thick moist paste.
14 / 25
What happens to the magnetic field generated by a current-carrying wire when the electric current is stopped?
When the current stops flowing, the magnetic effect disappears, and the compass needle returns to its original direction.
15 / 25
For practical applications, what core material is typically inserted into a current-carrying coil to make the resulting electromagnet stronger?
For practical applications, most electromagnets have an iron core to make them stronger.
16 / 25
In the internal structure of a typical dry cell, which component acts as the negative terminal?
The dry cell consists of a zinc container which acts as a negative terminal.
17 / 25
Which type of cell is described as a ‘single use cell’, meaning once the chemicals are used up, it must be disposed of?
The dry cell is a single use cell, meaning once it is used up, it has to be disposed of, unlike rechargeable batteries.
18 / 25
What is the term for the generation of heat in conductors due to the flow of electric current?
Generation of heat in conductors due to flow of electric current is known as the heating effect of electric current.
19 / 25
What is the primary purpose of lifting electromagnets used on cranes in factories and scrap yards?
Lifting electromagnets are used in factories and scrap yards to move, lift, and sort heavy iron/steel objects. The magnet is controlled by switching the current ON and OFF.
20 / 25
What is the primary cause of Earth behaving like a giant magnet?
Deep inside the Earth, the movement of liquid iron in the core creates electric currents, which in turn generate a magnetic field.
21 / 25
In a Voltaic cell, what is the liquid substance in which the metal plates (electrodes) are partly dipped?
The plates, called electrodes, are partly dipped in the liquid called an electrolyte, which is usually a weak acid or salt solution.
22 / 25
Which two Italian scientists are associated with the Voltaic or Galvanic cell, based on their observations of electricity generated by metals and liquid?
The Voltaic or Galvanic cells get their names from two Italian scientists, Alessandro Volta and Luigi Galvani.
23 / 25
A current carrying coil that behaves as a magnet is called an:
A current carrying coil that behaves as a magnet is called an electromagnet.
24 / 25
In electric heating appliances like a room heater, what is the rod or coil of wire called?
Many household appliances contain a rod or a coil of wire, called a heating element.
25 / 25
Which scientist is credited with the discovery in 1820 that electricity and magnetism are linked, observing that an electric current produced a magnetic field?
Hans Christian Oersted (1777–1851), a professor in Denmark, observed and published his findings that an electric current indeed produced a magnetic field.
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