Science Worksheet (Set 14)
Topic: Electricity and Magnetism
Grade: VII
Q1. Answer the following questions:
a. Why are filament-type electric bulbs not power-efficient? Name any two types of electric lighting devices which are much more energy-efficient than filament-type bulbs.
– Filament-type bulbs are not power-efficient because a large portion of the electrical energy is converted into heat instead of light.
– Energy-efficient alternatives:
1. LED (Light Emitting Diode) bulbs
2. CFL (Compact Fluorescent Lamp) bulbs
– Energy-efficient alternatives:
1. LED (Light Emitting Diode) bulbs
2. CFL (Compact Fluorescent Lamp) bulbs
b. Identify the device shown in the picture.
Fuse
i. What is the purpose of this device in a circuit?
A fuse protects electrical circuits from excessive current by melting and breaking the circuit when there is an overload.
ii. What would happen if this device is not present in an overloaded circuit?
– Without a fuse, excessive current in the circuit could cause overheating, potentially leading to electrical fires.
– Electrical appliances may get damaged due to high current flow.
– Electrical appliances may get damaged due to high current flow.
c. Why is it necessary to use an electrolyte in the process of electrolysis? Can pure water undergo electrolysis without any additives?
– An electrolyte provides free ions that conduct electricity and allow chemical reactions to occur during electrolysis.
– Pure water is a poor conductor of electricity because it lacks free ions. Electrolysis of pure water requires the addition of an electrolyte (e.g., acid, salt, or base) to improve conductivity.
– Pure water is a poor conductor of electricity because it lacks free ions. Electrolysis of pure water requires the addition of an electrolyte (e.g., acid, salt, or base) to improve conductivity.
d. Explain why resistance increases when the temperature of a conductor increases.
– As temperature increases, the vibrations of metal atoms inside the conductor become more intense.
– This hinders the free movement of electrons, increasing the resistance to current flow.
– This hinders the free movement of electrons, increasing the resistance to current flow.
Q2. Case Study: Electromagnets
A factory uses an electromagnet made of a solenoid for lifting heavy metal objects. The solenoid is powered by a large battery.
a. Why is the solenoid used in this case instead of a permanent magnet?
– A solenoid can be turned on and off, allowing control over lifting and releasing metal objects.
– Permanent magnets have constant magnetism, making them less suitable for industrial applications where control is needed.
– Permanent magnets have constant magnetism, making them less suitable for industrial applications where control is needed.
b. What will happen if the solenoid is disconnected from the battery?
The electromagnet loses its magnetic properties, and the metal objects will fall.
c. Suggest two ways to make the solenoid lift heavier objects.
1. Increase the number of coils in the solenoid.
2. Increase the current flowing through the solenoid by using a stronger battery.
2. Increase the current flowing through the solenoid by using a stronger battery.