Science STD 6 Chapter 9: Electricity and Circuits - Exercises
1. Fill in the blanks:
-
A device that is used to break an electric circuit is called .............
a switch
-
An electric cell has ............. terminals.
two
2. Mark 'True' or 'False' for following statements:
-
Electric current can flow through metals.
True.
-
Instead of metal wires, a jute string can be used to make a circuit.
False.
-
Electric current can pass through a sheet of thermo Col.
False.
3. Explain why the bulb would not glow in the arrangement shown in Fig. 9.13.
The bulb will not glow in the arrangement shown because the two terminals of the bulb are connected to only one terminal of the electric cell. An electric circuit requires a complete path for the current to flow from the positive terminal of the cell to its negative terminal, and this arrangement does not provide that path.
4. Complete the drawing shown in Fig. 9.14 to indicate where the free ends of the two wires should be joined to make the bulb glow.
The two free ends of the wires should be connected to the two terminals of the electric cell. One wire should be connected to the positive terminal and the other to the negative terminal to complete the circuit and make the bulb glow.
5. What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.
An electric switch is a simple device used to either break or complete an electric circuit. It allows us to turn an electrical appliance on or off. Some examples of gadgets with built-in switches are a television, fan, lamp, and radio.
6. Would the bulb glow after completing the circuit shown in Fig. 9.14 if instead of a safety pin we use an eraser?
No, the bulb would not glow. An eraser is an insulator, meaning it does not allow electric current to pass through it. Therefore, if it is used to complete the circuit, the path for the current will be broken, and the bulb will not light up.
7. Would the bulb glow in the circuit shown in Fig. 9.15?
No, the bulb would not glow. The wires are connected to only one terminal of the electric cell, which does not create a complete circuit for the current to flow. The bulb needs a connection to both the positive and negative terminals of the cell to glow.
8. Using the "conduction tester" on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.
The object is a conductor. A conductor is a material that allows electric current to pass through it. Since the bulb in the conduction tester glowed, it means that the material completed the circuit, allowing the current to flow, which is the property of a conductor.
9. Why should an electrician use rubber gloves while repairing an electric switch at your home? Explain.
An electrician uses rubber gloves because rubber is an electrical insulator. It does not allow electric current to pass through it, protecting the electrician from receiving an electric shock. This is a crucial safety measure to prevent severe injuries or death.
10. The handles of the tools like screwdrivers and pliers used by electricians for repair work usually have plastic or rubber covers on them. Can you explain why?
The handles of tools used by electricians have plastic or rubber covers because plastic and rubber are insulators. The tools themselves are made of metal, which is a conductor. The insulating covers prevent the electrician's hands from coming into direct contact with the metal and the live wire, thereby protecting them from electric shocks.
Suggested Activities
1. Imagine there were no electric supply for a month. How would that affect your day to day activities and others in your family? Present your imagination in the form of a story or a play.
Outline: This is a creative writing and problem-solving activity. Students must imagine a world without electricity and describe how it would impact daily life. The story or play should highlight the dependency on electricity for everything from lighting and cooking to communication and entertainment. It helps students appreciate the role of electricity in modern life.
2. For your friends, you may set up a game "How steady is your hand?"...
Outline: This is a hands-on activity that uses a simple circuit to create a game. The goal is to move a metal key through a wire loop without touching it. If the key touches the wire, the circuit is completed, and the bulb glows. The activity demonstrates the concept of electrical conduction and the completion of a circuit in a fun, interactive way.