**NUMERICAL - Electricity and its
effects For (Class X)**
1. A resistance of 6 ohms is connected in series with another
resistance of 4 ohms. A potential difference of 20 volts is applied across the
combination. Calculate the current through the circuit and potential difference
across the 6 ohm resistance.

2. Calculate the number of electrons constituting one coulomb of
charge per second through any cross section of a conductor.

3. How much work is done in moving a charge of 2 C across two
points having a potential difference of 12 V ?

4. How much energy is given to each coulomb of charge passing through
a 6 V battery ?

5. Calculate the work done in moving a charge of 5 Coulombs from a
point at a potential of 210 Volts to another point at 240 Volts.

7. When a particle of charge 10 µC is brought from infinity to a
point P, 2.0 mJ work is done by the external forces. What is the potential at P
?

9. How many electrons pass through a lamp in one minute if the
current be 200 mA?

10. Calculate the current supplied by a cell if the amount of
charge passing through the cell in 4 seconds is 12 C ?

11. A 2 Volt cell is connected to a 1 Ω resistor. How many
electrons come out of the negative terminal of the cell in 2 minutes?

12. a) How much current will an electric bulb draw from a
220 V source, if the resistance of the bulb filament is 1200 Ω ?

b) How much current will an electric heater coil draw from a
220 V source, if the resistance of the heater coil is 100 Ω ?

13. The potential difference between the terminals of an electric
heater is 60 Volts when it draws a current of 4 Ampere from a source. What current
will the heater draw if the potential difference is increased to 120
Volt.

14. A torch bulb when cold has 1Ω resistance. It draws a current
of 0.3 Ampere when glowing from a source of 3 V. Calculate the resistance of
the bulb when glowing and explain the reason for the difference in
resistance.

## 2 comments:

1.Calculate the current and resistance of a 100 W ,200V electric bulb.

Solution:

Power,P = 100W

Voltage,V = 200V

Power p = VI

Current I = P = 100 = 0.5A

V 200

Resistance R = V = 200 = 400W.

I 0.5

2. Calculate the power rating of the heater coil when used on 220V supply taking 5 Amps.

Solution:

Voltage ,V = 220V

Current ,I = 5A,

Power,P = VI = 220 × 5

= 1100W = 1.1 KW.

3.A circuit is made of 0.4 Ω wire,a 150Ω bulb and a 120Ω rheostat connected in series.Determine the total resistance of the resistance of the circuit.

Solution:

Resistance of the wire = 0.4Ω

Resistance of bulb = 150Ω

Resistance of rheostat = 120Ω

In series,

Total resistance ,R = 0.4 + 150 +120

= 270.4Ω

4.In the circuit shown in fig .find the current,voltage drop across each resistor and the power dissipated in each resistor.

Total resistance of the circuit = 2 + 6 +7

R = 15 Ω

Voltage ,V = 4 5V

Circuit current ,I = V = 45 = 3A

R 15

Voltage drop across 2Ω resistor V1 = I R1

= 3 × 2 = 6 Volts.

Voltage drop across 6Ω resistor V2 = I R2

= 3 × 6 = 18 volts.

Voltage drop across 7Ω resistor V3 = I R3

= 3 × 7 = 21 volts.

Power dissipated in R1 is P1 = P R1

= 32 × 2 = 18 watts.

Power dissipated in R2 is P2 = I2 R2.

= 32 × 6 = 54 watts.

Power dissipated in R3 is P3 = I2 R3.

= 32 × 7 = 63 watts.

Can I get the answers for the questions above

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