CBSE > Class 07 > Science | CBSE Board | Homework Help

A concave mirror can form a real and inverted image. When the object is placed very close to the mirror, the image formed is virtual, erect and magnified.

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What's the difference between convex and concave lens?

Posted by Subhra Santoshi Pradhan 4 years, 3 months ago

CBSE > Class 07 > Science

1 answers

Sia ? 4 years, 3 months ago

A convex lens is thicker at the centre and thinner at the edges. A concave lens is thicker at the edges and thinner at the centre. Due to the converging rays, it is called a converging lens. Due to the diverging rays, it is called a diverging lens.

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What is water cycle

Posted by Aj Styles 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Ayush Kushwaha 7 years, 9 months ago

The process by which water get evaporate and condense with the process of evaporation and condensation. In this process water evaporate and go in air then condense. The water come back to land this is called water cycle

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What is Topsoil

Posted by Vivek Raj 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Yuv Raj 7 years, 9 months ago

The topmost layer of the soil

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Topoil

Posted by Vivek Raj 7 years, 9 months ago

CBSE > Class 07 > Science

0 answers

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Is heat absorbed or evolved in condensation of vapours

Posted by Parmveer Singh 7 years, 9 months ago

CBSE > Class 07 > Science

0 answers

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Why can't we use copper wire for making an electic fuse

Posted by Vishu Sharma 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Yuv Raj 7 years, 9 months ago

We use the copper bt in less quantity becoz copper is a good conductor of heat and if we use copper in electric fuse then it will be melted down quickly from heat

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what is common unit of the measurement of temperature

Posted by Mohit Mishra 7 years, 9 months ago

CBSE > Class 07 > Science

2 answers

Yuv Raj 7 years, 9 months ago

Not only Celsius there were Fahrenheit also a common unit of the measurement of temperature

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Abhinav Rana 7 years, 9 months ago

celcius is the common unit of temprature

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Hello there Can you tell ☺ me that tomorrows my science paper short circuit and overloading please help

Posted by Ishika Jain 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Abhinav Rana 7 years, 9 months ago

short circuit-

A short circuit (sometimes abbreviated to short or s/c) is an <a href="https://en.wikipedia.org/wiki/Electrical_network" title="Electrical network">electrical circuit</a> that allows a <a href="https://en.wikipedia.org/wiki/Electric_current" title="Electric current">current</a> to travel along an unintended path with no or a very low <a href="https://en.wikipedia.org/wiki/Electrical_impedance" title="Electrical impedance">electrical impedance</a>. The electrical opposite of a short circuit is an "<a href="https://en.wikipedia.org/wiki/Open-circuit_voltage" title="Open-circuit voltage">open circuit</a>", which is an infinite resistance between two nodes. It is common to misuse "short circuit" to describe any electrical malfunction, regardless of the actual problem.

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If u dip an Iron nails into a copper sulphate solution it comes out copper plated but if you dip a copper nail in iron sulphate will it be iron plated??

Posted by Chitra Manghani 7 years, 9 months ago

CBSE > Class 07 > Science

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what is excretory system

Posted by Rahul Naik 7 years, 9 months ago

CBSE > Class 07 > Science

0 answers

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What is the speed of light

Posted by Soham Mittal 7 years, 9 months ago

CBSE > Class 07 > Science

2 answers

Yuv Raj 7 years, 9 months ago

3000000 m/s

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Jash Makadia 7 years, 9 months ago

from sun it take 8.20 sec

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Why whale and dolphin come on the surface of water to breathe

Posted by Khushi Patel 7 years, 9 months ago

CBSE > Class 07 > Science

2 answers

Yuv Raj 7 years, 9 months ago

Becoz they hv lungs

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Joan Mariam Jijo 7 years, 9 months ago

Because they are mammals

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What is the nature of intermolecular forces

Posted by Tushar Kumar 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Kritika Trehan 7 years, 9 months ago

Intermolecular forces (IMFs) are the forces which mediate interaction between molecules, including forces of attraction or repulsion which act between molecules and other types of neighboring particles, e.g., atoms or ions. Inter-molecular forces are weak relative to intramolecular forces – the forces which hold a molecule together. For example, the covalent bond, involving sharing electron pairs between atoms, is much stronger than the forces present between neighboring molecules. Both sets of forces are essential parts of force fields frequently used in molecular mechanics.

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What are indicators

Posted by Tawseef Ahmad 7 years, 9 months ago

CBSE > Class 07 > Science

2 answers

Shreya Jha 7 years, 9 months ago

Indicator is a special type of substance which use to check whether a substance is acidic or basic.

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Vivek R 7 years, 9 months ago

indicators are the substances which will help us to identify acid and base

there are 2 types of indicators.natural and artificial

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If a toy car runs towards a plane mirror with a speed of 2 m/s,then at what speed will the image of the car run towards it ?

Posted by Harsh Raj 7 years, 9 months ago

CBSE > Class 07 > Science

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Why does a flame of the candle always burn upwards?

Posted by Harsh Raj 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Kritika Trehan 7 years, 9 months ago

Flame is basically packet of hot gases. It is visible to us because of its temperature. Consider a kerosene burner, a hydrocarbon is burning and producing co2, water and heat.

For any hydrocarbon..
CxH2y + (x+1/2y) O2 ---> x CO2 + y H2O + HEAT

Now this heat of combustion heats the surrounding gas. This gas may have temperature varying from 200 to 1500 deg. C

Now these heated gases are around burning location (reaction location eg, candle tip), it can go up or down??

But when gases are heated their kinetic energy increases and distance between molecules increases correspondingly, which makes gas rare and less denser.

As this gas is lighter it will tend to go up, and denser cold surrounding air will come down to replace it.

As flame travels up it gets diluted and temperature falls, it become invisible to our eyes.

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What is a galviniasation

Posted by Harsh Kaushal 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Amit Kumar Pusty 7 years, 9 months ago

The process deposting of desired metter on the surface of other metal is called galvalisation

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Why does a chapatti inflates when it is heated?

Posted by Harsh Raj 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Yuv Raj 7 years, 9 months ago

Becoz heat makes the chapati with hot air

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Why are holes made in huge hoardings?

Posted by Harsh Raj 7 years, 9 months ago

CBSE > Class 07 > Science

1 answers

Dinesh Mishra 7 years, 9 months ago

We know that air exerts pressure. Due to high pressure it may tear. So to give a complete air passage holes are made in hoardings

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Why is the word AMBULANCE written as downwards on vehicles

Posted by Harsh Raj 7 years, 9 months ago

CBSE > Class 07 > Science

2 answers

Shreya Jha 7 years, 8 months ago

Because of laterally inverting phenomena

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Kritika Trehan 7 years, 9 months ago

So that drivers ahead of it on the road can read
it (correctly) as AMBULANCE in their rear-view
mirrors, and yield the right of way.
If the word was not reversed, the drivers of the
cars ahead of the vehicle would see:
"ECNALUBMA."
Of course, if it has flashing lights and sirens
going, they would yield to it anyway. Perhaps
this was done so that drivers would not mistake
an ambulance for a police vehicle with similar
lights.

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Will iron filings get attracted to an electromagnet when it is switched on or off ?Explain

Posted by Harsh Raj 7 years, 9 months ago

CBSE > Class 07 > Science