CBSE Class 7 Science Important Questions Chapter 10 - Electric Current and Its Effects

1. What is an electric circuit?
An electric circuit is a closed path through which electric current flows from a power source, such as a battery, through connected components and back to the source. The circuit allows electricity to power devices like bulbs, fans, or motors. The main components of a simple circuit include a power source, connecting wires, and devices that use electricity, creating a loop for continuous current flow.

2. Explain the role of a switch in an electric circuit.
A switch controls the flow of electric current in a circuit. When the switch is "on," it completes the circuit, allowing current to pass through and power devices. When the switch is "off," it breaks the circuit, stopping the current and turning off any connected devices. This simple mechanism helps control the use of electricity efficiently and safely.

3. What is electric current?
Electric current is the flow of electric charge through a conductor, usually carried by electrons moving through a wire. It is measured in amperes (A) and represents the amount of charge passing a point in the circuit per second. Electric current is essential for operating electrical devices, from light bulbs to complex machines, by providing the energy required for their operation.

4. What happens when an electric current passes through a bulb?
When electric current flows through a bulb, it passes through a thin filament made of tungsten, which offers resistance to the flow of current. This resistance causes the filament to heat up, producing light and heat. This effect of producing light due to electric current is known as the heating effect of current, and it is the basic principle behind incandescent bulbs.

5. Describe the heating effect of electric current.
The heating effect of electric current occurs when current flows through a conductor, generating heat due to the resistance offered by the conductor. The more the resistance, the more heat produced. This effect is used in devices like electric heaters, irons, and toasters, where heat is needed for their functioning. It is also the reason why wires heat up when carrying too much current.

6. What is the magnetic effect of electric current?
The magnetic effect of electric current is the phenomenon where a current passing through a conductor creates a magnetic field around it. This effect can be observed by placing a compass near a current-carrying wire; the compass needle will deflect, indicating a magnetic field. This principle is used in electromagnets, electric motors, and generators, where magnetic fields are needed.

7. How does an electromagnet work?
An electromagnet is created by wrapping a coil of wire around an iron core and passing an electric current through the coil. The current generates a magnetic field, which magnetises the iron core, making it act as a magnet. Unlike permanent magnets, electromagnets can be turned on or off with the electric current, making them useful in various applications like cranes, electric bells, and door locks.

8. What are some uses of electromagnets?
Electromagnets are widely used due to their controllable magnetic field. They are used in cranes for lifting heavy metallic objects, in electric bells and buzzers to create sound, and in motors for generating rotational motion. They are also used in medical devices like MRI machines, where strong, temporary magnetic fields are essential.

9. Explain the function of an electric fuse.
An electric fuse is a safety device that protects electrical circuits from excessive current. It consists of a thin wire with a low melting point that melts and breaks the circuit if the current exceeds a safe level. This prevents overheating and potential fires by stopping the flow of electricity and safeguarding appliances and users from damage or injury.

10. Why does the fuse wire melt when there is an excess current?
The fuse wire melts due to its low melting point material. When excess current flows through the fuse, it generates heat due to resistance in the wire. The heat quickly builds up, causing the fuse wire to melt and break the circuit, which stops the flow of electricity and protects the appliances from further damage.

11. Describe how a simple electric circuit is constructed.
A simple electric circuit is constructed with a power source like a battery, connecting wires, and a load like a bulb. The wires are connected from the battery terminals to the bulb, completing the loop. When connected, the electric current flows from the positive terminal of the battery, through the wires, lighting the bulb, and returns to the negative terminal, forming a closed circuit.

12. How is the electric current measured, and what is its unit?
Electric current is measured using an ammeter, an instrument that calculates the flow of current in amperes (A). It is connected in series with other components in the circuit to measure the amount of charge passing through the circuit per second. Amperes, the SI unit of current, indicate the rate of electric flow.

13. What happens to a bulb if the circuit is broken?
If the circuit is broken, it is incomplete, and electric current cannot flow through it. As a result, the bulb will not light up because there is no current passing through its filament. A broken circuit can occur if there is a loose connection, a cut wire, or an open switch in the circuit.

14. What is a conductor, and why is it important in electric circuits?
A conductor is a material that allows electric current to flow through it easily, such as metals like copper and aluminium. Conductors are essential in electric circuits as they provide a path for current to travel from one component to another, making it possible for devices to operate.

15. Why do electric appliances like irons and heaters get warm?
Electric appliances like irons and heaters get warm due to the heating effect of electric current. As electric current flows through their heating elements, resistance generates heat, warming up the appliance. This heat is then used for tasks like ironing clothes or warming up a room.

16. What are insulators, and why are they used in electrical devices?
Insulators are materials that do not allow electric current to pass through them, like rubber, plastic, or wood. They are used in electrical devices to cover wires and prevent accidental electric shocks. Insulators provide safety by keeping current confined to the intended path within the circuit.

17. Explain how an electric bell works.
An electric bell works by using an electromagnet. When the switch is pressed, current flows through the coil, magnetising an iron strip that pulls a hammer to hit the bell. This breaks the circuit, and the hammer returns to its original position, allowing the process to repeat, creating a continuous ringing sound.

18. Why are circuit breakers used in modern electrical systems?
Circuit breakers are used to automatically stop the flow of current when it exceeds safe limits. They act like reusable fuses and help prevent damage from overloading, short circuits, or power surges by breaking the circuit. Unlike fuses, circuit breakers can be reset after tripping, making them more convenient.

19. How does the direction of current flow affect the magnetic field in a wire?
The direction of electric current determines the direction of the magnetic field around the wire. When the current’s direction is reversed, the magnetic field’s direction also reverses. This property is used in electric motors and other devices to control motion.

20. What is the role of an ammeter in a circuit?
An ammeter measures the amount of electric current flowing through a circuit. It is connected in series with other components and displays the current in amperes, helping to monitor and control the circuit’s performance.

21. How does current cause a wire to become an electromagnet?
When electric current passes through a coil of wire wrapped around an iron core, it generates a magnetic field, turning the iron core into a magnet. This temporary magnet is called an electromagnet and can be turned on or off by controlling the current.

22. What safety measures should be followed when using electric appliances?
Safety measures include using insulated tools, keeping water away from appliances, not overloading sockets, and using fuses or circuit breakers. These practices reduce the risk of electric shocks, fires, or damage to devices and help ensure the safe use of electricity.

23. How can the magnetic effect of current be demonstrated only?
The magnetic effect of current can be demonstrated by passing current through a wire placed near a compass. The compass needle will deflect due to the magnetic field created by the current, showing that electric current can produce magnetism.

24. Why are electric circuits important for appliances to work?
Electric circuits allow electric current to flow from a power source to the appliance, enabling it to operate. A complete circuit provides a continuous path for the current, while a broken circuit will stop the current and prevent the appliance from working.

25. Describe a real-life use of the heating effect of electric current.
The heating effect of electric current is used in devices like electric stoves and heaters. When current flows through their heating elements, it produces heat, which can then be used for cooking or warming a space. This effect is also found in toasters, irons, and kettles.

5 Important Topics of Class 7 Science Chapter 10 You Shouldn’t Miss!

Benefits of Class 7 Chapter 10 Science Important Questions

• Focuses on Main Ideas - Important questions cover essential topics like circuits, effects of current, and safety, making these ideas easier to understand and remember.

• Helpful for Exams - Practising these questions helps students get familiar with possible exam questions, making them feel more prepared and confident.

• Improves Understanding - Answering questions about electric circuits and current effects helps students understand and apply what they’ve learned in practical ways.

• Good for Quick Revision - Important questions are a quick way to go over the chapter’s main points, making revision easier before exams.

• Increases Comfort with Science Topics - Regular practice with these questions helps students feel more comfortable discussing and working on Science topics in class.

Conclusion

Important Questions for Chapter 10 - Electric Current and Its Effects gives students a clear view of how electricity works and how it’s used in our daily lives. By learning about circuits, electric currents, and important safety measures, students understand the basics of electrical devices around them. This chapter helps students see the impact of electricity in science and everyday technology, sparking curiosity about the world of energy and how it powers so many things we rely on.

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