1. Consider the following statements and choose the correct option:
Statement I: Fluorescent lights work by passing an electric current through a gas or vapour, which emits visible light.
Statement II: Incandescent bulbs produce light by passing an electric current through a tungsten filament, causing it to glow.
a) Statement I is correct but statement II is incorrect.
b) Statement I is incorrect but statement II is correct.
c) Both statements are correct.
d) Both statements are incorrect.
Answer: c) Statement I is correct because fluorescent lights do work by passing an electric current through a gas or vapour, which emits visible light.
Statement II is also correct because incandescent bulbs produce light by passing an electric current through a tungsten filament, causing it to glow
2. In which of the following devices is the magnetic effect of electric current utilised to convert electrical energy into mechanical energy?
a) Solar panel
b) Loudspeaker
c) X-ray machine
d) Laser printer
Answer: b) Loudspeakers utilise the magnetic effect of electric current to convert electrical energy into mechanical energy. An electric current passing through a coil of wire in the loudspeaker interacts with a permanent magnet, creating a varying magnetic field. This varying magnetic field then causes a cone to vibrate, producing sound waves and converting electrical energy into mechanical energy for the purpose of generating sound.
3. Which of the following factors affect the heating effect of an electric current?
I. The resistance of the material
II. The voltage applied
III. The duration of the current flow
a) Only I
b) Only II
c) Only I and III
d) I, II, and III
Answer: d) All three factors mentioned affect the heating effect of an electric current:
I. The resistance of the material: Higher resistance leads to more heat generation.
II. The voltage applied: Higher voltage results in increased heat production.
III. The duration of the current flow: The longer the current flows through a material, the more heat is generated.
4. Choose the correct option to complete the statement
The __________ effect of electric current is responsible for the corrosion of metal objects over time.
a) heating
b) magnetic
c) lighting
d) Chemical
Answer: d) The Chemical effect of electric current is responsible for the corrosion of metal objects over time. When an electric current passes through a metal object, it can cause a chemical reaction that leads to the gradual breakdown or deterioration of the metal surface, resulting in corrosion.
5. Which statement best describes the difference between an electromagnet and a permanent magnet?
a) Electromagnets are always stronger than permanent magnets.
b) Electromagnets can be turned on and off while permanent magnets cannot.
c) Electromagnets generate electricity, while permanent magnets do not.
d) Electromagnets have multiple poles, while permanent magnets have a single pole.
Answer: b) The main difference between an electromagnet and a permanent magnet is that an electromagnet is created by passing an electric current through a coil of wire, which generates a magnetic field. This magnetic field can be controlled by turning the current on or off. In contrast, a permanent magnet produces a magnetic field naturally and does not require an electric current. It retains its magnetism without the need for an external power source and cannot be turned on or off.
