Electicity
One Marks Questions
Answer: The flow of charges constitutes electric current. Electric current is the rate of flow of electric charges.
Answer: A continuous and closed path of an electric current is called electric circuit.
Answer: Charge of one electron = 1.6 × 10-19 c
Answer:
a. ampere
b. volt
Answer: The electric potential difference between two point in an electric circuit is defined as the work done to move a unit charge from one point from the other.
Answer:
The total resistance Rs= R1 +R2 + R3
Answer:
Electric Iron , Electric heater, electric toaster, electric oven, electric kettle and electric heater.
Answer: The bulbs are usually filled with chemically inactive nitrogen and argon gases to prolong the life of filament.
Answer: Electric power is defined as the rate at which electric energy is dissipated or consumed in an electric circuit.
Two Marks Questions
Answer: The Joules law of heating states that The heat produced in a resistor is
i. directly proportional to the square of current for a given resistor.
ii. Directly proportional to the resistance for a given current.
iii. Directly proportional to the time for which current flows through resistor.
Answer: The electric heating is used to produce light in an electric bulb. The filament in the bulb gets hot due to heating effect of electric bulb and emits light.
Answer: The bulbs are usually filled with chemically inactive nitrogen and argon gases to prolong the life of filament.
Answer:
Ohm’s law states that “The potential difference, V , across the ends of a given metallic wire in an electric circuit is directly proportional to the current flowing through it, provided its temperature remains the same.”
Answer:
Work = 100 J
charge = 20 coulomb
We know that potential difference =
Potential difference =
= 5 volt
Answer:
The rheostat is the variable resistor. It means its resistance can be varied. The rheostat is used to change the value of current in a circuit without changing the voltage source.
Answer:
The motion of electrons in an electric circuit constitutes an electric current. The electrons, however, are not completely free to move within a conductor. They are restrained by the attraction of the atoms among which they move. Thus, motion of electrons through a conductor is retarded by its resistance.
Answer:
(a) We are given,
V = 220 V
R = 1200 Ω
we have I =
current I =
current I = = 0.18 A
(b) We are given,
V = 220 V
R = 100 Ω
current I =
current I = = 2.2 A.
Three and Four Marks Questions
Answer:
i. Length of a conductor :
The resistance of a uniform metallic conductor is directly proportional to length (l) of a conductor.
ii. Area of cross section :
The resistance of a conductor is directly proportional to its area of cross section(A)
iii. Nature of material :
The resistance of conductor depends on nature of material which it is made of.
iv. Temperature :
Resistance of conductor increases with increase in temperature.
Answer:
When heating at max rate,
power, P = 840W
V = 220V
We know P = VI
⇒ 840 = 220 × I
⇒ I =
⇒ I = 4 A
R = V/I =
So current = 4 A and resistance = 55 Ω
When heating at minimum rate,
power, P = 360 W
V = 220 V
We know P = VI
⇒ 360 = 220 × I
⇒ I =
⇒ I = 1.636 A
R =
So current = 1.636 A and
resistance = 134.45 Ω
Answer:
Potential difference = V = 5 V
Current = I = 500 mA = 0.5 A
i. Power = V X I
= 5x0.5
= 2.5 W
ii. Reistance = R = ?
By Ohm's law: V = IR
R =
R =
=
= 10 Ω
iii. Energy consumed when it is lighted for 4 hours
Energy = Power x time
Energy = 2.5x4x60x60
Energy = 36000 joules/sec
