In an electroscope,
Question: In an electroscope, if a negatively charged body is brought in contact with the metal dip, the strips of the electroscope diverge. If now another charged object carrying equal amount of positive charge is brought in contact with the clip, what will happen? Solution: If a positively charged object is brought in contact with the metal clip of an electroscope, the negative charge given earlier to the clip will be neutralised and the diverged strips will contract....
Read More →Explain how does lightning conductor
Question: Explain how does lightning conductor protects a building from getting struck by lightning. Solution: Lightning conductor does not allow the charge to accumulate on a building and transfers all the charges to the earth, protecting the building from being struck by lightning....
Read More →The angles of a quadrilateral are in AP, and the greatest angle is double
Question: The angles of a quadrilateral are in AP, and the greatest angle is double the least. Express the least angle in radians. Solution: Let the smallest term be x, and the largest term be 2x Then AP formed= x, ?, ?, 2x So $\mathrm{S}_{\mathrm{n}}=\frac{\mathrm{n}}{2}[2 \mathrm{a}+(\mathrm{n}-1) \mathrm{d}]$ $\mathrm{S}_{\mathrm{n}}=\frac{\mathrm{n}}{2}[\mathrm{a}+(\mathrm{a}+(\mathrm{n}-1) \mathrm{d})]=\frac{\mathrm{n}}{2}[$ First term $+($ Last term $)]$ $360^{\circ}=4 / 2[x+2 x] \ldots . ...
Read More →You might have observed on a dry day
Question: You might have observed on a dry day that when you touch the screen of a television or computer monitor (with picture tube), you get a slight shock. Why does it happen? Solution: It happens because the television screen or computer monitor are charged and have static charges accumulated on them and when we touch them with our hands which are uncharged, the charges transfer through our hands and we get a slight shock....
Read More →If the materials used for constructing
Question: If the materials used for constructing a building were good conductors, do you think lightning will strike the building. Will the lightning conductor be still required to be installed in the building? Solution: Lightning will not strike the building because charge separation cannot take place in conductors and so, all the lightning falling on the building will reside bn the surface of the building. So, there is no need of installing any lightning conductor because all the work of light...
Read More →If air and cloud were good
Question: If air and cloud were good conductors of electricity, do you think lightning could occur? Explain. Solution: No, there will not be any lightning at all because charge separation cannot take place in conductors. So, all the charges collected at the clouds will continuously transfer through air, i.e. charge will not accumulate on cloud and so, there will be no lightning....
Read More →During the construction of a building,
Question: During the construction of a building, the lightning conductor was left hanging in the air by mistake. Would the lightning conductor be still effective? Explain Solution: Lightning conductor will not work, if left hanging in the air because in order to work, it must be connected to the ground by using any metal (copper) plate, so that the charge can pass through it to the ground....
Read More →Plastic straws A and B are rubbed
Question: Plastic straws A and B are rubbed with dry cotton cloth. What will happen, if they are brought near each other? Solution: When both the straws are rubbed with a dry cotton cloth, they will acquire the similar charge and hence they will repel each other....
Read More →If a charged plastic straw is
Question: If a charged plastic straw is brought near another uncharged plastic straw, what will happen? Solution: The charged plastic straw will attract another uncharged plastic straw, when brought near to it because charges of different kind attract each other....
Read More →Is it possible to predict
Question: Is it possible to predict the occurrence of an earthquake? Solution: No, scientists have tried lots of different ways of predicting earthquake but none have been successful so far. They have a pretty good idea of where an earthquake is most likely to hit but they still cannot tell exactly when it will happen....
Read More →State whether the following statements are True/False
Question: State whether the following statements are True/False (i) Earthquakes occur anytime all over the world. . (ii)The plates of the outermost layer of the earth are always in continuous motion. (iii)Tremors on the earth can also be caused by the eruption of a volcano. (iv)The process of electric discharge cannot occur between clouds and the earth. (v) Bathing outdoors should be avoided during thunderstorm. Solution: (i) True, it is not possible to predict the occurrence of an earthquake. (...
Read More →Consider the list of terms given below:
Question: Consider the list of terms given below: (i) Tsunami (ii) Landslides (iii) Floods (iv) Lightning Earthquakes can cause (a) (i), (ii) and (iii) (b) (ii) and (iv) (c) (ii), (iii) and (iv) (d) (iii) and (iv) Solution: (a) Earthquake is a sudden shaking or trembling of the earth due to the collision between the earths plates or brushing past of one plate over the other. It can cause Tsunami, floods and landslides....
Read More →Major earthquakes are less likely to occur in
Question: Major earthquakes are less likely to occur in (a) North-East India (b) Rajasthan (c) Rann of Kutch (d) Orissa Solution: (d) .Major earthquakes are less likely to occur in Orissa. The most threatened areas in India are Kashmir, Western and Central Himalayas, the whole of North-East, Rann of Kutch, Rajasthan and Indo-Gangetic Plane....
Read More →The outermost layer of the earth is called
Question: The outermost layer of the earth is called (a) mantle (b) outer core (c) crust (d) inner core Solution: (c) The outermost layer of the earth is carted crust. It is also known as earths crust....
Read More →Consider the list of terms given below:
Question: Consider the list of terms given below: (i) Seismic zone (ii) Fault zone (iii) Mantle (iv) Inner core The boundaries of the earths plate are known as (a) (i) and (ii) (b) (i) and (iii) (c) (iii) and (iv) (d) (ii), (iii) and (iv) Solution: (a) Since earthquakes are caused by the movement of plates, the boundaries of the plates are weak zones where earthquakes are more likely to occur. These weak zones are also known as seismic or fault zones....
Read More →The earth’s plate responsible
Question: The earths plate responsible for causing earthquake is (a) the crust of the earth (b) the mantle of the earth (c) the inner core of the earth (d) the outer core of the earth Solution: (a) An earthquake is a. sudden shaking or trembling of the earth which lasts for a very short time. It is caused by the disturbance deep down inside the uppermost layer of the earth called the crust....
Read More →A wire of length 121 cm is bent so as to lie along the arc of a circle of
Question: A wire of length 121 cm is bent so as to lie along the arc of a circle of radius 180 cm. Find in degrees; the angle subtended at the centre by the arc. Solution: will be in degrees. Arc-length can be given by the formula : $\theta / 360^{\circ} \times 2 \pi r$ Hence it is given that $121 \mathrm{~cm}$ is the arc length. $\Rightarrow 121=\theta / 360^{\circ} \times 2 \pi r$ $=121=\theta / 360^{\circ} \times 2 \times 22 / 7 \times 180$ $=121=\theta / 360^{\circ} \times 360 \times 22 / 7$...
Read More →Which of the following is not likely
Question: Which of the following is not likely to cause tsunami? (a) A major nuclear explosion under sea (b) Earthquake (c) Volcanic eruption (d) Lightning Solution: (d) Tsunami refers to the powerful sea waves generated due to the disturbance under the sea. It is not likely to occur in case of lightning, because lightning is an electric spark caused by the accumulation of charges in clouds....
Read More →Two charged objects are brought close
Question: Two charged objects are brought close to each other. Choose the most appropriate statement from the following options (a) They may attract (b) They may repel (c) They may attract or repel depending on the type of charges they carry (d) There will be no effect Solution: (c) Two charged objects may attract, if they carry opposite charges, while they repel, if they carry similar charges....
Read More →The movement of the earth’s
Question: The movement of the earths plates causes (a) cyclones (b) lightning (c) earthquake (d) thunderstorms Solution: (c) When the earths plates brush past one another or undergo collision, causes earthquake. An earthquake can cause huge damage to buildings, dams, etc....
Read More →A train is moving on a circular curve of radius 1500 m at the rate of 66 km
Question: A train is moving on a circular curve of radius 1500 m at the rate of 66 km per hour. Through what angle has it turned in 10 seconds? Solution: Radius = 1500 m Train speed at rate of $66 \mathrm{~km} / \mathrm{hr}=18.33 \mathrm{~m} / \mathrm{s}$ Therefore, Distance covered in 1 second $=18.33 \mathrm{~m}$ Distance covered in 10 second $=18.33 \times 10=183.33 \mathrm{~m}$ We know that $\theta=$ Distance $/$ radius $\theta=183.33 / 1500$ $=0.122$ radian Therefore $\theta=0.122 \times \f...
Read More →Electric current is to be passed
Question: Electric current is to be passed from one body to another. For this purpose, the two bodies mbst be joined by I (a) cotton thread (b) plastic string (c) copper wire (d) rubber band Solution: (c) Two bodies must be joined by any conducting wire, i.e. copper wire for the flow of current....
Read More →An electroscope is a device
Question: An electroscope is a device which is used to find if an object is (a) charged (b) magnetic (c) free of cracks (d) hot Solution: (a) An electroscope is a device, which is used to test whether an object is charged or not.It consists of closely placed two metallic strips. When both the strips are charged with similar charges, they repel each other and become wide open....
Read More →A wheel makes 180 revolutions in 1 minute
Question: A wheel makes 180 revolutions in 1 minute. Through how many radians does it turn in 1 second? Solution: Given that Number of revolutions per minute = 180 Then per second, it will be $=180 / 60=3$ We know that In one complete revolution, the wheel turns at an angle of $2 \pi_{\text {rad. }}$ Then for 3 complete revolutions, it will take $3 \times 2 \pi=6 \pi$ radians....
Read More →The large hand of a clock Is 42 cm long.
Question: The large hand of a clock Is 42 cm long. How many centimetres does its extremity move in 20 minutes? Solution: For 20 minutes $=\theta=4 \times 30^{\circ}=120^{\circ}$ We know that l = r $\mathrm{I}=42 \times 120 \times \frac{\pi}{180}=28 \times \frac{22}{7}=88$ Therefore, the length is equal to 88 cm....
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