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Two bulbs of 100W and 40W are connected in series. The current through the 100W bulb is 1A. The current through the 40W bulb will be: a) 0.4A b) 0.6A c) 0.8A d) 1

d) 1A Given P1=100W,P2=40W in series, i=1A In series , same current will flow in both bulb. A circuit is said to be connected in series when the... View Article

At the time of short circuit, the electric current in the circuit : (a) vary continuouslyn (b) does not change (c) reduces substantially (d) increases heavily

d) increases heavily When the plastic insulation of live and neutral wires gets torn somehow and touches each other, then due to this direct... View Article

When an object is kept within the focus of a concave mirror, an enlarged image is formed behind the mirror. This image is: (a) real (b) inverted (c) virtual and inverted (d) virtual and erect

(d) virtual and erect A concave mirror is a mirror that is curved inward in the middle. It is also known as converging mirrors, due to the fact... View Article

The laws of reflection hold true for : (a) plane mirrors only (b) concave mirrors only (c) convex mirrors only (d) all reflecting surfaces

(d) all reflecting surfaces The laws of reflection hold true for all the reflecting surfaces, i.e. all mirrors (either plane or spherical)... View Article

The chemical formula of plaster of Paris is a) CaSO4. 2H2O b) CaS04.H2O c) CaS04. 1/2H2O d) 2CaS04.H2O

b) CaSO4.2H2O The compound plaster of Paris is made by heating gypsum at 120 degree Celsius. The chemical formula for the plaster of paris... View Article

Baking soda is a mixture of : (a) Sodium carbonate and acetic acid (b) Sodium carbonate and tartaric acid (c) Sodium hydrogen carbonate and tartaric acid (d) Sodium hydrogen carbonate and acetic acid

(c) Sodium hydrogen carbonate and tartaric acid Baking soda is a mixture of sodium hydrogen carbonate and tartaric acid. It is used to increase... View Article

In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution : (A) exchange of atoms takes place(B)exchange of ions takes place(C) a precipitate is produced (D) an insoluble salt is produced The correct option is : (a) (B) and (D) (b) (A) and (C) (c) only (B) (d) (B), (C) and (D)

(d) (B), (C) and (D) In a double displacement reaction such as the reaction between sodium sulphate solution and barium chloride solution,... View Article

When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper sulphide is obtained and the sulphuric acid so formed remains in the solution. The reaction is an example of a : (a) Combination reaction(b) Displacement reaction (c) Decomposition reaction (d) Double displacement reaction

(d) Double displacement reaction When hydrogen sulphide gas is passed through a blue solution of copper sulphate, a black precipitate of copper... View Article

Calcium oxide reacts vigorously with water to produce slaked lime. CaO(s)+H2O(l)→Ca(OH)2(aq) This reaction can be classified as: (A) Combination reaction (B) Exothermic reaction (C) Endothermic reaction (D) Oxidation reaction Which of the following is the correct option?

A and B CaO(s)+H2O(l)→Ca(OH)2(aq) A combination reaction is a reaction where two or more elements or compounds combine to form a single... View Article

Why is the maximum concentration of pesticides found in human beings?

The maximum concentration of pesticides is found in human beings because humans comprise the topmost level into the food chain, and in the... View Article

List two common signs of sexual maturation in boys and girls.

The common signs of sexual maturation in boys and girls are: (i) Growth of excessive hairs on body parts such as pubic area, armpits, and face.... View Article

The change in magnetic field lines in a coil is the cause of induced electric current in it. Name the underlying phenomenon.

The change in magnetic field lines in a coil is the cause of induced electric current in it, and this phenomenon is known as Electromagnetic... View Article

Name a cyclic unsaturated cyclic compound

An example of a cyclic unsaturated compound is Cyclobutene. Ringed structures called cyclic hydrocarbons may be formed by hydrocarbons. Since... View Article

An object is placed at a distance of 10 cm from optical centre of a convex lens of focal length 5 cm. Draw a labelled ray diagram to show the formation of image in this case.

(i) Here the focal length f is 5 cm then 2f will be 10 cm (2×10), and object is placed 10 cm from the lens, means the object is at 2F′.Thus, when... View Article

Write the relationship among the object distance (u), image distance (v) and the focal length (f) of a (i) Spherical lens (ii) Spherical mirror

The relation between the object distance (u), the image distance (v) and the focal length (f) of a spherical mirror (a concave or convex mirror)... View Article

Define the following terms : (i) Power of a lens (ii) Principal focus of a concave mirror

It is the Ability of a lens to converge or diverge light rays/reciprocal of focal length of the lens.If the focal length is given in meters (m),... View Article

An object is placed perpendicular to the principal axis of a convex mirror of focal length 10 cm. The distance of the object from the pole of the mirror is 10 cm. Find the position of the image formed.

Focal length, f = 10cm Object distance, u = −10cm (object distance is always taken negative as it is on the left side) To find: Position of the... View Article

A concave mirror of focal length 10 cm can produce a magnified real as well as virtual image of an object placed in front of it. Draw ray diagrams to justify this statement.

(a) A concave mirror of focal length 10 cm can produce a magnified real image when the object is placed between the centre of curvature C and... View Article

A current of 500 mA flows in a series circuit containing an electric lamp and a conductor of 10 Ω when connected to 6 V battery. Find the resistance of the electric lamp.

Current, I = 500 mA = 0.5 A (converted milliampere to ampere) Resistance of the conductor, RC = 10Ω Potential... View Article

Find the ratio of resistances of two copper rods X and Y of lengths 30 cm and 10 cm respectively and having radii 2 cm and 1 cm respectively.

We have to find ratio of resistance of two copper rods Length of wire X = 30 cm Length of wire Y = 10 cm Radius of wire X = 2 cm Radius of... View Article

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