Electricity Science - Electricity

1. What is meant by saying that the potential difference between two points is 1 volt? Name a device that helps to measure the potential difference across a conductor.
2. Why does the connecting cord of an electric heater not glow hot while the heating element does?
3. Electrical resistivities of some substances at $20^{0}\text{C}$ are given below:

1. Among silver and copper, which one is a better conductor? Why?
2. Which material would you advise to be used in electrical heating devices? Why?

1. Name an instrument that measures electric current in a circuit. Define the unit of electric current.
2. What do the following symbols mean in circuit diagrams?

3. An electric circuit consisting of a 0.5 m long nichrome wire XY, an ammeter, a voltmeter, four cells of 1.5 V each and a plug key was set up.

1. Draw a diagram of this electric circuit to study the relation between the potential difference maintained between the points ‘X’ and ‘Y’ and the electric current flowing through XY.
2. Following graph was plotted between V and I values:

1. Which among iron and mercury is a better conductor?
2. Which matcrial is the best conductor?

1. The 2C of charge is flowing through a conductor in 100ms, the current in the circuit will?
    
2. Define electric current? what is the SJ unit of electric current.
    
3. The potential difference between the two terminals of battery, if 100 joules of work is required to transfer 20 coulombs of charge from one terminal of the battery to other will?

4. a) Then number of electrons flowing per second in a conductor if I A current is passing through it?
   b) The voltage can be written as.

1. The energy dissipated by the heater is E. When the time of operating the heater is doubled, the energy dissipated will?
    
2. The power of a lamp is 60W. The energy consumed in 1 minute will?
    
3. The electrical refrigerator rated 400W operates 8 hours a day. The cost of electrical energy is ₹ 5 per kWh. Find the cost of running the refrigerator for one day?
   OR
4. Calculate the energy transformed by a 5A current flowing through a resistor of $2\Omega$ for 30 minutes?

1. Both A and R are true, and R is correct explanation of the assertion.
2. Both A and R are true, but R is not the correct explanation of the assertion.
3. A is true, but R is false.
4. A is false, but R is true.

1. Which among iron and mercury is a better conductor?
2. Which matcrial is the bestconductor?

The rate of flow of charge is called electric current. The SJ unit of electric current is Ampere (A). The direction of flow of current is always opposite to the direction of flow of electrons in the current. The electric potential is defined as the amount of work done in bringing a unit positive test charge from infinity to a point in the electric field. The amount of work done in bringing a unit positive test charge from one point to another point in an electric field is defined as potential difference.

$\text{V}_{\text{AB}}=\text{V}_{\text{B}}-\text{V}_\text{A}=\frac{\text{W}_{\text{BA}}}{\text{q}}$

The SJ unit of potential and potential difference is volt.

1. The 2C of charge is flowing through a conductor in 100ms, the current in the circuit will?
   
   
2. Define electric current? what is the SJ unit of electric current.
   
   
3. The potential difference between the two terminals of battery, if 100 joules of work is required to transfer 20 coulombs of charge from one terminal of the battery to other will?

                                                 OR

4. a) Then number of electrons flowing per second in a conductor if I A current is passing through it?
   b) The voltage can be written as.

The obstruction offered by a conductor in the path of flow of current is called resistance. The SJ unit of resistance is ohm (Q). It has been found that the resistance of a conductor depends on the temperature of the conductor. As the temperature increases, the resistance also increases. But the resistance of alloys like mangnin, Constantin and nichrome is almost unaffected by temperature. The resistance of a conductor also depends on the length of conductor and the area of cross-section of the conductor. More be the length, more will be the resistance, more be the area of cross-section, lesser will be the resistance.

1. Which is not will desired in material being used for making electrical wires?
   
   
2. What is a resistance?
   
   
3. Which resistance of alloys will unaffected by temperature?
                          OR
4. A wire of resistance $20\Omega$ is cut into 5 equal pieces. The resistance of each part will be?

The heating effect of current is obtained by transformation of electrical energy in heat energy. Just as mechanical energy used to overcome friction is covered into heat, in the same way, electrical energy is converted into heat energy when an electric current flows through a resistance wire. The heat produced in a conductor, when a current flows through it is found to depend directly on (a) strength of current (b) resistance of the conductor (c) time for which the current flows. The mathematical expression is given by $\text{H} = \text{I}^2\text{Rt}.$

The electrical fuse, electrical heater, electric iron, electric geyser etc. all are based on the heating effect of current.

1. What are the properties of heating element?
   
   
2. What are the properties of electric fuse?
   
   
3. When the current is doubled in a heating device and time is halved, the heat energy produced will be?
                                            OR
4. A) A fuse wire melts at 5 A. It is is desired that the fuse wire of same material melt at 10 A. The new radius of the wire will be.
   
   B) When a current of 0.5A passes through a conductor for 5 min and the resistance of conductor is $10\Omega$ the amount of heat produced will be.

The electrical energy consumed by an electrical appliance is given by the product of its power rating and the time for which it is used. The SI unit of electrical energy is Joule. Actually, Joule represents a very small quantity of energy, and therefore it is inconvenient to use where a large quantity of energy is involved. So for commercial purposes we use a bigger unit of electrical energy which is called kilowatt-hour. 1 kilowatt-hour is equal to 3.6 × 10⁶ joules of electrical energy.

1. The energy dissipated by the heater is E. When the time of operating the heater is doubled, the energy dissipated will?
   
   
2. The power of a lamp is 60W. The energy consumed in 1 minute will?
   
   
3. The electrical refrigerator rated 400W operates 8 hours a day. The cost of electrical energy is ₹ 5 per kWh. Find the cost of running the refrigerator for one day?
                                   OR
4. Calculate the energy transformed by a 5A current flowing through a resistor of $2\Omega$ for 30 minutes?
   

1. What is meant by saying that the potential difference between two points is 1 volt? Name a device that helps to measure the potential difference across a conductor.
2. Why does the connecting cord of an electric heater not glow hot while the heating element does?
3. Electrical resistivities of some substances at $20^{0}\text{C}$ are given below:

Answer the following questions in relation to them:

1. Among silver and copper, which one is a better conductor? Why?
2. Which material would you advise to be used in electrical heating devices? Why?