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83 questions · self-marked practice — reveal the answer and mark yourself.

Question 11 Mark
The headlights of a car have reflectors behind the bulb. What is the function of reflectors?
Answer
The reflector helps in reflecting the light into a focussed area.
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Question 21 Mark
In any electric circuit, when the switch is on and the current flows through it why do the wire, switches, bulb or devices become hot?
Answer
This is because electric energy changes into heat energy.
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Question 31 Mark
Give one activity to prove that air is an insulator.
Answer
Take an electric circuit, keep the terminals unconnected in the air. The bulb do not glow, as air is an insulator and does not allow the current to flow through it.
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Question 41 Mark
Name the scientist who invented electric cell and the scientist who invented electric bulb.
Answer
Electric cell: Alessandro Volta.
Electric bulb: Thomas Alva Edison.
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Question 51 Mark
Identify conductors and insulators from the following:Eraser, paper, matchstick, copper wire, pencil lead, polythene
Answer
Conductors: Copper wire, pencil lead.
Insulator. Eraser, paper, matchstick, polythene.
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Question 61 Mark
Define conductors and insulators. Give one example of each.
Answer
A conductor is that which easily allows the passage of current through it. Example: Aluminium or any metal.
An insulator is that which does not allow the passage of current through it. Example: Rubber.
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Question 71 Mark
Mention two advantages of a dry cell.
Answer
$1.$ It converts chemical energy into electrical energy.
$2.$ It is light and small in size.
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Question 91 Mark
Write one use of insulators.
Answer
Insulators are used in making switchboard, handles of testers, screw drivers.
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Question 101 Mark
What is open circuit?
Answer
An electric circuit in which electrical contact at any point is broken is called open circuit.
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Question 151 Mark
What is the direction of flow of current in a dry cell?
Answer
The current flows in closed circuit from $+ve$ to $-ve$ terminal of cell.
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Question 161 Mark
Using the“conduction tester” on an object it was found that the bulb begins to glow. Is that object a conductor or an insulator? Explain.
Answer
Yes, if the object is good conductor of electricity then current will pass through conduction tester and the bulb will glow. Hence the object will be a conductor of electricity.
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Question 171 Mark
Would the bulb glow in the circuit shown in Fig. $12.11.$
Image
Answer
Yes, the electric circuit is closed so the bulb will glow.
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Question 181 Mark
Would the bulb glow after completing the circuit shown in Fig. $12.9$ if instead of safety pin we use an eraser?
Answer
No, since eraser is an insulator so it does not allow the current to pass. Hence the bulb will not glow.
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Question 191 Mark
What is the purpose of using an electric switch? Name some electrical gadgets that have switches built into them.
Answer
Electric switch is used to make electric circuit open or closed for a particular appliance and hence with the help of a switch we can use an appliance according
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Question 201 Mark
Explain why the bulb would not glow in the arrangement shown in fig
Image
Answer
The bulb would not glow in the arrangement shown in figure because the one end of tester/screw driver is made up of plastic which does not allow the electric current to flow through it.
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Question 221 Mark
During a clear night, try to observe the Big Dipper $3-4$ times at , an interval of $2$ to $3$ hours. Also try to locate the Pole Star each time. Does the Big Dipper appear to move? Draw a rough sketch to illustrate this, mentioning the time in each case.
Answer
The Big Dipper appears to move around the Pole Star due to the rotation of the Earth. Over a few hours, its position changes, making it seem as if it is rotating around the Pole Star.
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Question 231 Mark
You can see stars fading away at dawn and appearing f at dusk. During the day we do not see the stars. Explain why?
Answer
During the day, the Sun’s bright light outshines the stars, making them invisible to our eyes. The atmosphere scatters the sunlight, creating the blue sky and masking the faint light of the stars.
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Question 241 Mark
An artist’s representation of the Solar System is given in Figure. Is the order of the planets correct? If not, write the correct order in the boxes in the figure.
Image
Answer
The order of the planets in the figure is not correct. The correct order from the Sun is: Mercuiy, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.
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Question 261 Mark
How many types of electric circuit are there? Define them.
Answer
There are two types of electric circuit:
$(a)$ Open electric circuit
$(b)$ Closed electric circuit
$(a)$Open electric circuit: The circuit in which electrical contact at any point is broken is called open electric circuit.
$(b)$Closed electric circuit: The circuit in which electric current flows from one terminal of a cell or battery to the other is called a closed circuit.
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Question 271 Mark
What is electric circuit?
Answer
The diagram that shows the path of electric current is called electric circuit.
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Question 281 Mark
What Is the name of Chandrayaan $3$ mission’s lander and the rover?
Answer
Chandrayaan $3$ mission’s lander is named Vikram and the rover Pragyan.
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Question 291 Mark
What Is the name of the successful mission by Indta which demonstrated end-toend capability in safe landing and roving on the lunar surface?
Answer
Chandrayaan-$3$ demonstrated end-to-end capability in safe landing and roving on the lunar surface.
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Question 301 Mark
What is the scientific study of universe called?
Answer
The scientific study of universe is called Astronomy.
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Question 311 Mark
Define Universe.
Answer
The Universe is a large space consisting of celestial bodies like the stars, planets, galaxy, dust and gases.
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Question 321 Mark
Why is our galaxy calledMilky Way?
Answer
Our galaxy is called the Milky Way because it appears as a milky hand of light in the sky when we see it in a really dark area.
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Question 341 Mark
What is the shape of the Milky Way Galaxy?
Answer
Our Milky Way Galaxy is a spiral galaxy having a whitish broadand. It looks like a spinning pinwheel when viewed from top or bottom.
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Question 361 Mark
Why is Venus called the Twin Planet?
Answer
Venus is considered as ‘Earth’s-twin’ because its size and shape are very much similar to that of the earth.
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Question 371 Mark
What is the other name of outer planets and name them?
Answer
Outer planets are also called Jovian planets. They are- Jupiter, Saturn, Uranus and Neptune.
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Question 381 Mark
What is the other name of inner planets and name them?
Answer
Inner planets are also called Terrestrial planets, They are – Mercury, Venus, Earth and Mars.
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Question 391 Mark
What are artificial satellites used for?
Answer
Artificial satellites are used for weather forecasting, long distance communication and remote sensing.
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Question 401 Mark
Why is Jupiter called the Stormy Planet?
Answer
Jupiter revolves around itself with a great speed; hence Jupiter is called the Stormy planet.
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Question 411 Mark
When is ‘National Space Day’ celebrated in India?
Answer
‘National Space Day’ is celebrated on August 23rd every year.
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Question 421 Mark
What is a Dwarf Planet?
Answer
A small sized celestial body that revolves independently around the sun is called the dwarf planet.
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Question 431 Mark
Which planet is called “morning or evening star and why?
Answer
Venus is usually seen shining brightly at dawn and dusk, and is commonly called the Morning Star or the Evening Star, even though it is not a star,
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Question 441 Mark
Which planet is known as the “Red Planet” and why?
Answer
Mars is called the Red Planet because it appears red. This is because the soil on Mars is reddish in colour.
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Question 471 Mark
How many planets in the solar system are made of gas? Name them.
Answer
Four planets are made out of gas and they are also referred to as gas giants. They are Jupiter, Saturn, Uranus, and Neptune.
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Question 511 Mark
Why is the Earth called a blue planet?
Answer
From the outer space, the earth appears blue because its three- fourths surface is covered by water. It is, therefore, called a blue planet.
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Question 521 Mark
What is meant by the ‘Solar System’?
Answer
The sun, eight planets, satellites and some other celestial bodies known as asteroids and meteoroids form the solar system.
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Question 541 Mark
How do astronomers use constellations?
Answer
Astronomers use constellations as a way to identify and- locate stars and other celestial objects in the night sky, aiding navigation and observation.
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Question 551 Mark
What are the other names of Pole Star?
Answer
Polaris/Dhruv Tara/ North Star/ Guiding Star are the other names of Pole Star.
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Question 561 Mark
Identify the following constellations:
Image
Answer
$(a)$ Ursa Major/Big Dipper
$(b)$ Ursa Minor/Little Dipper
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Question 571 Mark
What causes stars to rise and set?
Answer
This occurs due to Earth’s rotation which is spinning around its own axis.
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Question 581 Mark
What is Universe?
Answer
The Universe is a large space consisting of celestial bodies like the stars, planets, galaxy, dust and gases.
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Question 591 Mark
What is the distance between the Sun and the Earth?
Answer
The distance of the Sun from the Earth is about $150$ million km.
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Question 611 Mark
Which device is used to observe faint stars which are not visible to the naked eye?
Answer
Powerful telescopes are used to observe faint stars that are not visible to the naked eye.
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Question 621 Mark
A star is ten light years away from the earth. Suppose it brightens up suddenly today. After how much time shall we see this change?
Answer
We will see the change seen after $10$ years
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Question 641 Mark
Which star is nearest to us after the Sun?
Answer
Proxima tentauri is the star nearest to us after the Sun.
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Question 661 Mark
What is a shooting star?
Answer
A shooting star is actually a meteor burning up in Earth’s atmosphere, causing a streak of light in the sky.
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Question 671 Mark
What is a constellation?
Answer
A constellation is a group of stars that form a recognizable pattern in the sky.
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Question 681 Mark
Solve the riddles: I’m the planet that everyone calls “Red,” But really my soil is rust-colored instead. Look up and you may spot me in the sky, I’m the orange- colored dot, way up high. Which planet am I?
Answer
Mars
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