Exercise
E. Answer the following questions:
Answer the following questions in one or two sentences.
Question: 1. What is electric current?
Answer: Electric current is the flow of electric charge through a conductor, typically measured in terms of the movement of electrons. It is responsible for powering electrical devices and is essential for the functioning of electrical circuits.
Question: 2. What is the SI unit of electric current?
Answer: The SI unit of electric current is the ampere (A). It represents the flow of one coulomb of charge passing through a conductor in one second.
Question: 3. What is fuse?
Answer: A fuse is a safety device used in electrical circuits that prevents excessive current flow. It consists of a thin wire that melts and breaks the circuit when the current exceeds a certain limit, thereby protecting the circuit and connected devices from damage.
Question: 4. What are the two effects of electric current?
Answer: The two primary effects of electric current are:
1. Heating Effect: When electric current passes through a conductor, it generates heat. This principle is utilized in devices like electric heaters and toasters.
2. Magnetic Effect: Electric current produces a magnetic field around the conductor, which is the basis for the operation of electromagnets and electric motors.
Answer the following questions in detail.
Question: 1. Draw a circuit diagram of a dry cell connected to a bulb through a switch. Mark the positive and negative terminals of the cells, and the direction of flow of electric current in the diagram.To illustrate a circuit with Answer: a dry cell, a bulb, and a switch, follow these steps:
1. Components:
– Dry Cell: Represents the power source.
– Bulb: Acts as the load that uses the electric current.
– Switch: Controls the flow of current.
2. Diagram:
– Draw a battery symbol for the dry cell, marking the positive (+) terminal at the top and the negative (-) terminal at the bottom.
– Connect a wire from the positive terminal to one terminal of the switch.
– From the other terminal of the switch, connect another wire to one terminal of the bulb.
– Finally, connect a wire from the other terminal of the bulb back to the negative terminal of the dry cell.
3. Direction of Current Flow:
– Indicate the direction of current flow with arrows: from the positive terminal of the dry cell, through the switch, into the bulb, and back to the negative terminal.
Question: 2. How can you increase the magnetic strength of a solenoid?
Answer: The magnetic strength of a solenoid can be enhanced through the following methods:
- Increase the Number of Turns: Adding more coils of wire around the core increases the magnetic field strength.
- Increase the Current: Using a higher current through the wire will strengthen the magnetic field.
- Use a Ferromagnetic Core: Placing a ferromagnetic material (like iron) inside the solenoid amplifies the magnetic field due to the core’s properties.
Question: 3. What is an electromagnet? Give three uses of electromagnets.
Answer: An electromagnet is a type of magnet in which the magnetic field is produced by an electric current. It consists of a coil of wire (solenoid) wound around a core material (often iron). When electric current flows through the coil, it generates a magnetic field.
Uses of Electromagnets:-
1. Electric Bells: Used to operate bells in doorbells or alarms.
2. Magnetic Cranes: Employed in scrapyards to lift heavy metal objects.
3. MRI Machines: Utilized in medical imaging to create detailed images of the body’s internal structures.
Question: 4. Explain the working of an electric bell.
Answer: The electric bell operates based on the principles of electromagnetism. Here’s how it works:
1. Components:
– Electromagnet: Creates a magnetic field when current flows.
– Hammer: A metal arm that strikes the bell.
– Spring: Returns the hammer to its original position.
– Switch: Controls the current flow.
2. Working Process:
– When the switch is pressed, electric current flows through the circuit, energizing the electromagnet.
– The electromagnet attracts the hammer, causing it to strike the bell, producing sound.
– As the hammer moves, it breaks the circuit, stopping the current flow and deactivating the electromagnet.
– The spring pulls the hammer back to its original position, closing the circuit again, and the process repeats, creating a ringing sound.
This cycle continues as long as the switch is held down, producing a ringing sound from the bell.