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The essential difference between an AC generator and a DC generator is that A) AC generator has an electromagnet while a DC generator has permanent magnet. B) DC generator will generate a higher voltage. C) AC generator will generate a higher voltage. D) AC generator has slip rings while the DC generator has a commutator.

Answer: (D) AC generator has slip rings while the DC generator has a commutator. A generator is a mechanical equipment which converts a... View Article

Several electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. How many lamps can be connected in parallel with each other across the two wires of 220 V line if the maximum allowable current is 5 A?

Given that Electric bulbs designed to be used on a 220 V electric supply line, are rated 10 W. Find out The number of lamps that can be... View Article

State which of the following situations are possible and give an example for each of these: (a) an object with a constant acceleration but with zero velocity. (b) an object moving in a certain direction with acceleration in the perpendicular direction.

Answer: (a) The given statement is possible. The word acceleration implies a change in the object's velocity. One example of this is vertical... View Article

Pick out the odd property of rhombic sulphur: 1) Rhombic sulphur exists as octahedral crystals. 2) The density of rhombic sulphur is 2.06 g/mL. 3) Rhombic sulphur is yellow solid with melting point 385.8K and is soluble in carbon disulphide and insoluble in water.

Rhombic sulphur is yellow solid with melting point 385.8K and is soluble in carbon disulphide and insoluble in water.... View Article

Mountains and hills differ on the basis of: 1) A mountain is created by faulting while hill is created by either faulting or erosion. 2) A mountain is often named whereas hill is often unnamed. 3) The altitude and elevation of hill is low while the altitude and elevation of mountain is high.

1) A mountain is created by faulting while hill is created by either faulting or erosion. The faulting, that happens because the rocks... View Article

Look at the activities listed below. Reason out whether work is done or not in the light of your understanding of the term ‘work’. a) Suma is swimming in a pond. b)A donkey is carrying a load on its back. c)A wind mill is lifting water from a well. d)A green plant is carrying out photosynthesis. e)An engine is pulling a train. f) Food grains are getting dried in the sun. g) A sailboat is moving due to wind energy.

Work is done whenever the given conditions are satisfied: A force acts on the body. There is a displacement of the body by the application... View Article

Let the resistance of an electrical component remains constant while the potential difference across the two ends of the component decreases to half of its former value. What change will occur in the current through it?

Answer: According to Ohm’s law V = IR where V= potential difference I= Current R = Resistance We can also modify the above equation as... View Article

Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 second and then turns around and jogs 100 m back to point C in another 1 minute. What are joseph€™s average speeds and velocities in jogging (a) from A to B and (b) from A to C?

Total Distance covered from AB = 300m Total time taken = 2—60+30s =150s Therefore, Average speed from AB= Total Distance/ Total Time =300/150m... View Article

(i) Straight angle (a) less than one-fourth a revolution (ii) Right angle (b) more than half a revolution (iii) Acute angle (c) half of a revolution (iv) Obtuse angle (d) one-fourth a revolution (v) Reflex angle (e) between and of a revolution (f) One complete revolution

Column A Column B (a)Straight angle 1 Less than one-fourth of a revolution (b)Right angle 2 More than half a revolution (c)Acute angle 3... View Article

Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

Answer: The law of conservation of energy states that energy can be neither created nor destroyed. It can only be converted from one form to... View Article

For the following statements, write T for True and F for False. (i) J.J. Thomson proposed that the nucleus of an atom contains only nucleons. (ii) A neutron is formed by an electron and a proton combining together. Therefore, it is neutral. (iii) The mass of an electron is about 1/2000 times that of proton. (iv) An isotope of iodine is used for making tincture iodine, which is used as a medicine.

Answer: (i) J.J. Thomson proposed that the nucleus of an atom contains only nucleons. (F) (ii) A neutron is formed by an electron and a proton... View Article

Following are some of the characteristics of animals:(i) Diets heavy on fruits (ii) White fur (iii) Need to migrate (iv) Loud voice (v) Sticky pads on feet (vi) Layer of fat under skin (vii) Wide and large paws (viii) Bright colours (ix) Strong tails (x) Long and large beak For each characteristic indicate whether it is adaptation for tropical rainforests or polar regions. Do you think that some of these characteristics can be adapted for both regions?

Adaptation is defined as the process where a species or an organism gradually becomes better acclimated to its environment. Adaptation is... View Article

Fill in the blanks: (a) A place where animals are protected in their natural habitat is called a-fill in the blank- (b) Species found only in a particular area are known as -fill in the blank- (c) Migratory birds fly to faraway places because of -fill in the blank- changes.

Solution: (a) A place where animals are protected in their natural habitat is called a sanctuary (b) Species found only in a particular area are... View Article

Classify the following as chemical or physical changes: (a) Cutting of trees (b) Melting of butter in a pan (c) Rusting of almirah (d) Boiling of water to form steam (e) Passing of electric current, through water and the water breaking down into hydrogen and oxygen gases (f) Dissolving common salt in water (g) Making a fruit salad with raw fruits (h) Burning of paper and wood

Answer: Physical change - A substance is said to undergo a physical change when only the physical properties such as the shape, size, colour,... View Article

Choose the odd one out for ideal gas. a) The molecules of ideal gas do not obey Newton’s laws of motion. b) An ideal gas consists of a large number of unidentical molecules. c) Ideal gases have perfectly elastic collisions. d) The molecules do not move in random motion.

Ideal gases have perfectly elastic collisions.... View Article

Choose the correct option. A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each (A) two revolutions (B) One revolution (C) half revolution (D) one-fourth revolution

Answer: (C) half revolution The direction of the induced current varies once every half revolution when a rectangular coil is rotated in a... View Article

A taxi-driver, filled his car petrol tank with 40 liters of petrol on Monday. The next day, he filled the tank with 50 liters of petrol. If the petrol costs Rs. 44 per liter, how much did he spend in all on petrol?

Given that Petrol filled on Monday = 40 liters Petrol filled on next day = 50 liters Cost of 1 liter petrol = Rs. 44 Find out We have to... View Article

A spherical mirror and a thin spherical lens have each a focal length of -15 cm. The mirror and the lens are likely to be (A) both concave (B) both convex (C) the mirror is concave and the lens is convex (D) the mirror is convex, but the lens is concave.

Answer: (A) both concave The distance from the lens to the focal point is called the focal length. For converging lenses, the focal length is... View Article

Arya, Abhimanyu and Vivek shared lunch. Arya has brought two sandwiches, one made of vegetable and one of jam. The other two boys forgot to bring their lunch. Arya agreed to share his sandwiches so that each person will have an equal share of each sandwich. (a) How can Arya divide his sandwiches so that each person has an equal share? (b) What part of a sandwich will each boy receive?

a) Since there are three people to eat, Arya should divide his sandwiches into 3 equal parts and give 1 part of each sandwich so that each person... View Article

An object thrown at a certain angle to the ground moves in a curved path and falls back to the ground. The initial and the final points of the path of the object lie on the same horizontal line. What is the work done by the force of gravity on the object?

Answer: Work is said to be done when a force applied to an object moves that object. Work done is generally referred to in relation to the force... View Article

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