Ch -12 The power of electricity- Extra questions.

Q 1. Give reason Why is tungsten used to make the filament of a bulb?

Ans - Tungsten has high melting point, it does not melt even when the filament glows at a very high temperature.

Q 2. What is terminal? In what way are the two terminals of the bulb useful?

Ans - Battery terminals are the electrical contacts used to connect wires to a single cell or multiple-cell battery.When the two terminals are joined to an electric cell, the electric current flows through the filament which gets heated up and starts glowing.

Q3. Define electric circuit

Ans - The complete path from one terminal of an electric cell through the bulb and back to the other terminal of the electric cell is called electric circuit.

Q 4. What do you understand by a fused bulb?

Ans - When the filament of a bulb breaks, the electric circuit is no more complete, since no current can pass through the filament now, the bulb does not glow and is thus called a fused bulb)

Q 5. List two points to explain advantages of using a secondary cell over a primary cell.

Ans - The major advantage of the secondary cell that it is rechargeable, and in the long run, may not cost at much as constantly replacing a primary cell.

Q 6. What type of a cells are used in the equipment shown below. Draw a circuit diagram for the shown equipment.

Ans – Dry cell is used in the given equipment. 

Q 7. Which of the following bulb will not glow in the arrangement shown in the figures? Give reason for each.

Ans – Bulb A will glow as circuit is correct and complete.

          Bulb B will not glow as one end of the wire is connected to glass of the bulb which is insultor and will not allow current to pass to the filament.

          Bulb C will not glow as two same terminals of the cells are connected which will not allow passage of current.

          Bulb D will not glow as two ends of the wires are connected to the same terminal of the bulb.

Q 8. Why solar panels are used as a source of electricity in the spacecrafts?

Ans -  Solar panels are devices that convert sunlight into electricity. In space most of the time, the most powerful source of light available is the Sun A solar panel is a collection of solar cells. Lots of small solar cells spread over a large area can work together to provide enough power to be useful. The more light that hits a cell, the more electricity it produces, so spacecraft are usually designed with solar panels that can always be pointed at the Sun.

Q 9. What will happen if we connect two cells instead of one in a circuit?

Ans-A cell or battery can push an electric current through a lamp. The bigger the voltage, the bigger the push. A bigger push gives a bigger current and the lamp shines more brightly. Each lamp is labelled with the biggest voltage it can survive. With too many volts, the current is too big and the lamp will burn out.

Q.10. Give reason: electric current flows from positive to negative.

Ans –Electrons have negative charge. Therefore they move from negative terminal to the positive terminal (i.e in the opposite direction to the conventional current). This is what is happening in the wires. However, we still use the convention that: electric current flows from positive to negative

Q 11. What happens in the eletric circuit?

Ans – In an electric circuit electric current flows. An electric current is a flow of electric charge around a circuit. The charge is already in the wires (carried by billions of tiny particles called electrons). This charge is evenly spread out through the wires. As soon as you close the switch, the cell starts to push on the charge. So all the charge starts moving at once.