By QB365 on 04 Oct, 2022
QB365 provides a detailed and simple solution for every Possible Creative Questions in Class 10th Science Subject -Electricity, English Medium. It will help Students to get more practice questions, Students can Practice these question papers in addition to score best marks.
10th Standard
Science
Define electric potential and potential difference.
What is the role of the earth wire in domestic circuits?
State Ohm’s law.
Distinguish between the resistivity and conductivity of a conductor.
What connection is used in domestic appliances and why?
An electric iron consumes energy at the rate of 420 W when heating is at the maximum rate and 180 W when heating is at the minimum rate. The applied voltage is 220 V. What is the current in each case?
A 100 watt electric bulb is used for 5 hours daily and four 60 watt bulbs are used for 5 hours daily. Calculate the energy consumed (in kWh) in the month of January.
A torch bulb is rated at 3 V and 600 mA. Calculate it’s
a) power
b) resistance
c) energy consumed if it is used for 4 hour.
A piece of wire having a resistance R is cut into five equal parts.
a) How will the resistance of each part of the wire change compared with the original resistance?
b) If the five parts of the wire are placed in parallel, how will the resistance of the combination change?
c) What will be ratio of the effective resistance in series connection to that of the parallel connection?
Water boils in an electric kettle in 15 mins after switching on. If the length of the heating wire is decreased to \(\frac{1}{3}\) of its initial value, then in how much time will the same amount of water boil with the same supply voltage?
Write any five electrical components used in electrical circuit and draw its symbol.
Kalaivani was watching at a metal pipe, one end of which is connected to a tank at the top of her building and the other end to the tap, which is near the ground level. She was admiring how the water flows from top to the bottom through the pipe. She went and asked her mother, who was an engineer.
(i) Also Kalaivani asked her mother that can she able to compare this with any other scientific concepts?
(ii) How would her mother have compared the resistance in a water pipe as well as in a conductor.
(iii) Give the expression for resistors connected in series and parallel.
Name any 5 components of a circuit. Write the uses and draw the symbols used.
Define the unit of resistance.
Differentiate series and parallel circuits.
a) What is Nichrome?
b) what are the characteristics of a good heating element?.
How does the earth wire serve as a protective conductor which saves us from electric shocks?
Write a note on LED Bulbs.
Write a note on seven segment display.
Answers
Electric potential : The electric potential at a point is defined as the amount of work done in moving a unit positive charge from infinity to that point against the electric force.
Electric potential difference : The electric potential difference between two points is defined as the amount of work done in moving a unit positive charge from one point to another point against the electric force.
(i) The earth wire provides a low resistance path to the electric current.
(ii) The earth wire sends the current from the body of the appliance to the Earth, whenever a live wire accidentally touches the body of metallic electric appliance.
(iii) Thus, the earth wire serves as a protective conductor, which saves us from electric shock.
According to Ohm's law, at a constant temperature, the steady current 'I' flowing through a conductor is directly proportional to the potential difference 'V' between the two ends of the conductor.
\(I\alpha V \Rightarrow\) V = IR
S.No |
Resistivity |
Conductivity |
---|---|---|
(i) |
It is the resistance of a |
The reciprocal of electrical |
(ii) | Its unit is ohm meter | Its unit is ohm-1 meter-1 |
(iii) | Resistivity is less for conductor than for insulators | Conductivity is more for conductors than for insulators. |
(iv) | ρ = RA / L | σ = 1 / ρ |
Parallel connection is used in domestic appliances.
Reason:
(i) Each appliance will get the full voltage.
(ii)The parallel circuit divides the current through the appliances.
(iii) Each appliance will get the proper current depending on its resistance.
(iv) Each of them can be put on / off independently.
Given:
Energy consumed when heating is maximum at the given rate \((P_{1})=420 \mathrm{~W}\)
Energy consumed when heating is minimum at a given rate \(P_{2}=180 \mathrm{~W}\)
Applied voltage = 220 V
Current in each case = ?
\(\mathbf{P}=\mathbf{V} \times \mathbf{I}\)
case (i) : \(\mathrm{I}_{1}=\frac{\mathrm{P}_{1}}{\mathrm{~V}}=\frac{420}{220}=1.9 \mathrm{~A}\)
case (ii) : \(\mathrm{I}_{2}=\frac{\mathrm{P}_{2}}{\mathrm{~V}}=\frac{180}{220}=\mathbf{0 . 8 1} \mathbf{A}\)
Given:
Power of the first electric bulb \(=100 \mathrm{~W}=100 / 1000=0.1 \mathrm{~kW}\)
Time = 5 hours
Power of the second electric bulb \(=60 \ \mathrm{watt}=\frac{60}{1000}=0.06 \mathrm{~kW}\)
Total number of bulbs = 4,
∴ 4 x 0.06 = 0.24 kW
Time = 5 hours.
Energy consumed in the month of January = ?
Energy = Power x time
Energy consumed by the first bulb in a day = 0.1 x 5 = 0.5 kWh
Energy consumed by the four 60 W bulb in a day =0.06 x 4 x 5 = 1.2 kWh
Total energy consumed by both the bulbs = 0.5 + 1.2 = 1.7 kWh
Total energy consumed in the month of January = 31 x 1.7 = 52.7 kWh
Given:
\(\mathrm{V}=3 \mathrm{~V} \)
\(\mathrm{I}=600 \mathrm{~mA}=600 \times 10^{-3} \mathrm{~A}, \quad \text { time }=4 \text { hours } \)
\(\text { Power }=?, \text { resistance }=?,\quad \text { energy =? }\)
(a) Power = \(\mathrm{V} \times \mathrm{I}\)
\(=3 \times 600 \times 10^{-3}=1.8 \mathrm{~W}\)
(b) Resistance \(=\frac{V}{I}\) [\(\because\) V = IR]
\(=\frac{3}{600 \times 10^{-3}}=5 \Omega\)
(c) Energy consumed in 4 hours
= \(\mathrm{P} \times \mathrm{t} \)
= 1.8 x 4 = 7.2 Wh
a) Wire is cut into 5 equal parts. Since all dimensions are same, resistance of each wire is equal and has a value = \(\frac {R}{5}\)
b) Formula for finding the effective resistance when connected in parallel is
\(\frac{1}{R_{p}^{\prime}}=\frac{1}{R_{1}}+\frac{1}{R_{2}}+\frac{1}{R_{3}}+\frac{1}{R_{4}}+\frac{1}{R_{5}}\)
Here, \(\mathrm{R}_{1}=\mathrm{R}_{2}=\mathrm{R}_{3}=\mathrm{R}_{4}=\mathrm{R}_{5}=\frac{\mathrm{R}}{5}\)
\(\frac{1}{R_{p}}=\frac{5}{R}+\frac{5}{R}+\frac{5}{R}+\frac{5}{R}+\frac{5}{R}\)
\(\frac{1}{R_{p}}=\frac{25}{R} \)
\(R_{p}=\frac{R}{25} \Omega\)
c) If the resistors are connected in series, then the effective resistance will be
\(\mathrm{R}_{\mathrm{s}}=\frac{\mathrm{R}}{5}+\frac{\mathrm{R}}{5}+\frac{\mathrm{R}}{5}+\frac{\mathrm{R}}{5}+\frac{\mathrm{R}}{5} \)
\(\mathrm{R}_{\mathrm{s}}=\frac{5 \mathrm{R}}{5}=\mathrm{R}\)
Ratio of effective resistance in series connection to that of the parallel connection is
\(\frac{R_{s}}{R_{p}}=\frac{R}{R / 25}=\frac{25}{1}\Rightarrow R_s:R_p=25:1\)
Supply Voltage is same
Amount of heat produced is also same
Time taken to heat water t = 15 min.
\(H=\frac { { V }^{ 2 } }{ R } .t\quad [H={ I }^{ 2 }Rt\Rightarrow (V=IR)\therefore I=\frac { V }{ R } ]\)
\(\therefore \frac { { R }_{ 1 } }{ { R }_{ 2 } } =\frac { { t }_{ 1 } }{ { t }_{ 2 } } \quad ...(1)\)
\(R\alpha l\quad \quad \quad [R=\rho \frac { l }{ A } ]\)
\(\frac { { R }_{ 1 } }{ { R }_{ 2 } } =\frac { { l }_{ 1 } }{ { l }_{ 2 } } \quad \quad \quad ...(2)\)
From (i) and (2)
\(\frac { { l }_{ 1 } }{ { l }_{ 2 } } =\frac { { t }_{ 1 } }{ { t }_{ 2 } } =\frac { 15 }{ { t }_{ 2 } } \quad \quad ....(iii)\)
\({ l }_{ 2 }=\frac { 1 }{ 3 } { l }_{ 1 }\Rightarrow \frac { { l }_{ 1 } }{ { l }_{ 2 } } =3\)
Sub in (iii) \(3=\frac { 15 }{ { t }_{ 2 } } \)
\(\therefore { t }_{ 2 }=\frac { 15 }{ 3 } =5min\)
Time taken to heat \(\frac{1}{3}\) length of the wire = 5 min
Component | Use Of The Component | Symbol Used | |
i) | A resistor of resistance R | Used to fix the magnitude of the current through the circuit | |
ii) | Variable resistor or Rheostat | Used to select the magnitude of the current through the circuit. | |
iii) | Ammeter | Used to measure the current. | |
iv) | Voltmeter | Used to measure the potential difference. | |
v) | Galvano meter | Used to indicate the direction of current. |
(i) Kalaivani's mother took a small PVC pipe which has water in it and held in a horizontal position. Water came out drop by drop. When she raised one of the ends of the pipe, the water through the other end came out with a greater speed. She said initially when I was holding the pipe in a horizontal position, pressure at the both the ends are same. So water did not come out. The difference in pressure (Pressure difference) between the two ends is zero. But when I raised one of the ends, the top end has high pressure, and the bottom end has low pressure. Due to this pressure difference, water came out with a faster rate. So compare a conductor or a wire to this PVC pipe The wire is connected to a battery, whose one end has higher potential and the other end has lower potential. Due to this difference in potential, electrons from negative terminal (lower potential end) flow towards the positive terminal (higher potential end). Here electron flow is compared with the water flow and the electric potential is compared with the pressure. Kalaivani felt very happy, after hearing her mother's genius explanation.
(ii) When Kalaivani asked how to understand about the concept of resistance from her mother's scientific explanations, her mother continued. If the water pipe is smooth inside, then there is no charge in the speed of flow of water. i.e., zero resistance. But when the pipe has some blocks inside at different points, the water changes its speed of flow at different points, likewise, whenever electrons flow inside the conductor, they may collide with each other, due to which their speed will be resisted (blocked), which forms as electrical resistance. Her explanation made Kalaivani satisfied.
(iii) When two resistors of resistances, R1 & R2 are connected in series to a battery source.
\({ R }_{ s }={ R }_{ 1 }+{ R }_{ 2 }\)
When R1 & R2 are connected in parallel,
\(\frac { 1 }{ { R }_{ p } } +\frac { 1 }{ { R }_{ 1 } } +\frac { 1 }{ { R }_{ 2 } } \Rightarrow \frac { 1 }{ { R }_{ p } } =\frac { { R }_{ 2 }+{ R }_{ 1 } }{ { R }_{ 1 }{ R }_{ 2 } } \)
\({ R }_{ p }=\frac { { R }_{ 1 }{ R }_{ 2 } }{ { R }_{ 1 }+{ R }_{ 2 } } \)
COMPONENT | USE OF COMPONENT | SYMBOL USED |
Resistor | Used to fix the magnitude of the current through a circuit. | |
Variable resistor or Rheostat | Used to select the magnitude of the current through a circuit. | |
Ammeter | Used to measure the current | |
Voltmeter | Used to measure the potential difference. | |
Galvanometer | Used to indicate the direction of the current. |
i) The SI unit of resistance is ohm.
ii) Resistance of a conductor is said to be one ohm, if a current of one ampere flows through it, when a potential difference of one volt is maintained across its ends.
S.NO |
CRITERIA |
SERIES |
PARALLEL |
i | Equivalent resistance | More than the highest resistance. | Less than the Iowest resistance. |
ii | Amount of current | Current is less as effective resistance is more. | Current is more effective resistance is less. |
iii | Switching ON/OFF | If one appliance is disconnected, others also do not work. | If one appliance is disconnected, others will work independently. |
a) Nichrome is an alloy of nickel and chromium.
b) A good heating element should have.
i) High resistivity
ii) High melting point
iii) Not easily oxidized.
i) In domestic circuits, a third wire called the earth wire having green insulation is usually connected to the body of the metallic electric appliance.
ii) The other end of the earth wire is connected to a metal tube or a metal electrode, which is buried into the Earth.
iii) This wire provides a low resistance path to the electric current.
iv) The earth wire sends the current from the body of the appliance to the Earth, whenever a live wire accidentally touches the body of the metallic electric appliance.
v) Thus, the earth wire serves as a protective conductor, which saves us from electric shocks.
i) An LED bulb is a semiconductor device that emits visible light when an electric current passes through it.
ii) The colour of the emitted light will depend on the type of materials used.
iii) With the help of the chemical compounds like Gallium Arsenide and
iv) Gallium phosphide, the manufacturer can produce LED bulbs that radiate red, green, yellow, and orange colours.
v) Displays in digital watches and calculators, traffic signals, street lights, decorative lights, etc., are some examples of the use of LEDs.
i) A 'Seven Segment Display' is the display device used to give an output in the form of numbers or text.
ii) It is used in digital meters, digital clocks, microwave ovens, etc
iii) It consists of 7 segments of LEDs in the form of the digit 8.
iv) These seven LEDs are named a, b, c, d, e, f, and g. An extra 8th LED is used to display a dot.