English Medium Class 10 - CBSE Question Bank Solutions

Decomposition reactions require energy either in the form of heat or light or electricity for breaking down the reactants. Write one equation each for decomposition reactions where energy is supplied in the form of heat, light and electricity

A student is unable to see clearly the words written on the black board placed at a distance of approximately 3 m from him. Name the defect of vision the boy is suffering from. State the possible causes of this defect and explain the method of correcting it.

Name the unit of electrical resistance and give its symbol.

Name the physical quantity whose unit is "ohm".

When a 12 V battery is connected across an unknown resistor, there is a current of 2.5 mA in the circuit. Calculate the value of the resistance of the resistor.

 Name the law which is illustrated by the above V−I graph.

Ohm's law gives a relationship between:

(a) current and resistance
(b) resistance and potential difference
(c) potential difference and electric charge
(d) current and potential difference

The unit of electrical resistance is:

(a) ampere
(b) volt
(c) coulomb
(d) ohm

Keeping the p.d. constant, the resistance of a circuit is halved. The current will become:

(a) one-fourth
(b) four time
(c) half
(d) double

The graph between V and I for a conductor is a straight line passing through the origin.

1. Which law is illustrated by such a graph?
2. What should remain constant in a statement of this law?

The graph between V and I for a conductor is a straight line passing through the origin. 

 What should remain constant in a statement of this law?

Fill in the following blank with suitable words: 

Resistance is measured in .............. The resistance of a wire increases as the length ..............; as the temperature ..............; and as the cross-sectional area .............. .

How should the two resistances of 2 ohms each be connected so as to produce an equivalent resistance of 1 ohm?

The resistors R₁, R₂, R₃ and R₄ in the figure given below are all equal in value. 

What would you expect the voltmeter A, B and C to read assuming that the connecting wires in the circuit have negligible resistance?

Four resistances of 16 ohms each are connected in parallel. Four such combinations are connected in series. What is the total resistance? 

How much energy is consumed when a current of 5 amperes flows through the filament (or element) of a heater having resistance of 100 ohms for two hours? Express it in joules.

 A resistance of 40 ohms and one of 60 ohms are arranged in series across 220 volt supply. Find the heat in joules produced by this combination of resistances in half a minute.

A solid substance P which is very hard is used in the construction of many buildings, especially flooring. When substance P is heated strongly, it decomposes to form another solid Q and a gas R is given out. Solid Q reacts with water with the release of a lot of heat to form a substance S. When gas R is passed into a clear solution of substance S, then a white precipitate of substance T is formed. The substance T has the same chemical composition as starting substance P.

1. What is substance P? Write its common name as well as chemical formula.
2. What is substance Q?
3. What is gas R?
4. What is substance S? What is its clear solution known as?
5. What is substance T? Name any two natural forms in which substance T occurs in nature.

The white solid compound A decomposes quite rapidly on heating in the presence of a black substance X to form a solid compound B and a gas C. When an aqueous solution of compound B is reacted with silver nitrate solution, then a white precipitate of silver chloride is obtained along with potassium nitrate solution. Gas C does not burn itself but helps burn other things.

1. What is compound A?
2. What is compound B?
3. What is gas C?
4. What do you think is the black substance X? What is its function?
5. What is the general name of substances like X?

What type of reaction is represented by the digestion of food in our body?