|
If you leave a piece of iron in the open for a few days, it acquires a film of brownish substance, called rust. Do you think rust is different from iron?
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0
|
4297
|
March 23, 2018
|
|
When the current is switched on through a wire, a compass needle kept nearby gets deflected from its north-south position. Explain
|
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0
|
4549
|
March 23, 2018
|
|
Give an example of a chemical reaction for each of the following situations: A change in colour is observed. A gas is evolved. Sound is produced. Formation of precipitate. Change of state from liquid to gas. Change of state from gas to liquid
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0
|
3565
|
March 23, 2018
|
|
How do short circuits occur?
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0
|
573
|
March 23, 2018
|
|
Write four uses of electromagnets
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0
|
642
|
March 23, 2018
|
|
On what factors does the strength of an electromagnet depend?
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0
|
2175
|
March 23, 2018
|
|
Give two examples for each of the following cases: Physical changes which are reversible. Physical changes which are not reversible. Chemical changes
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0
|
1248
|
March 23, 2018
|
|
On what factors does the heat produced in a wire depend?
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0
|
5451
|
March 23, 2018
|
|
What are electric fuses? Why are they important?
|
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0
|
1209
|
March 23, 2018
|
|
Will the compass needle show deflection when the switch in the circuit shown by figure given below is closed?
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0
|
1503
|
March 23, 2018
|
|
Name any two effects of electric current
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0
|
761
|
March 23, 2018
|
|
When chemical reaction takes place, what changes accompany the formation of new substances?
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0
|
1301
|
March 23, 2018
|
|
The figure below shows four cells fixed on a board. Draw lines to indicate how you will connect their terminals with wires to make a battery of four cells
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0
|
2309
|
March 23, 2018
|
|
Give example of two substances that can undergo physical and chemical changes, depending upon the conditions
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|
0
|
1110
|
March 23, 2018
|
|
Draw the circuit diagram to represent the circuit shown below
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0
|
3443
|
March 23, 2018
|
|
Why does a magnesium ribbon burn with a dazzling white flame?
|
|
0
|
2576
|
March 23, 2018
|
|
Draw in your notebook the symbols to represent the following components of electrical
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|
0
|
10608
|
March 23, 2018
|
|
Boojho made an electromagnet by winding 50 turns of wire over an iron screw
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|
0
|
3819
|
March 23, 2018
|
|
What is rust? How is it formed?
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|
0
|
5879
|
March 23, 2018
|
|
Why do we cover plug pin holes which are within the reach of children with cellotape or a plastic cover when not in use?
|
|
0
|
1617
|
March 23, 2018
|
|
How can iron articles be prevented from rusting?
|
|
0
|
634
|
March 23, 2018
|
|
Explain why rusting of iron objects is faster in coastal areas than in deserts
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|
0
|
1281
|
March 23, 2018
|
|
Name two electric devices for each where heating effect of current is used and magnetic effect of current is used
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|
0
|
5191
|
March 23, 2018
|
|
Explain how painting of an iron gate prevents it from rusting
|
|
0
|
1678
|
March 23, 2018
|
|
Can we use the same fuse in a geyser and a television set? Explain
|
|
0
|
1946
|
March 23, 2018
|
|
Explain why burning of wood and cutting it into small pieces are considered as two different types of changes
|
|
0
|
1818
|
March 23, 2018
|
|
How would you show that setting of curd is a chemical change?
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|
0
|
993
|
March 23, 2018
|
|
When a candle burns, both physical and chemical changes take place
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|
0
|
1337
|
March 23, 2018
|
|
With the help of Newton’s disc, prove that seven colours of the rainbow can be recombined and produce white light
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|
0
|
1319
|
March 23, 2018
|
|
When baking soda is mixed with lemon juice, bubbles are formed with the evolution of a gas
|
|
0
|
1579
|
March 23, 2018
|