Magnetic Effects Of Electric Current
(One Mark Question) Q.1 Why does the bulk of iron fillings stick to the ends of a bar magnet and not at its centre? Ans. Because at the ends magnetic strength is maximum and at centres magnetic strength is least. Q.2 If the frequency of A.C. is 50 Hz. Then how many times it is changing its direction in 1 second? Ans- 100 Times. Q.3 What is the pattern of the magnetic field lines around a straight conductor carrying current? Ans. Concentric circles Q.4 If the current is flowing in the direction of advancemet of screw, then what is the direction of magnetic field lines? Ans.In the direction of rotation of screw. Q.5 How can you say that the magnetic field is uniform inside the solenoid. Ans. Because field lines are parallel inside the solenoid. Q.6 Which property of a proton will change while it moves freely in a magnetic field? Ans. Momentum or Velocity. Q.7 According to Flemings right hand rule, which part of right hand indicate the movement of conductor? Ans. Thumb Q.8 If the no. of turns of a circular current carrying coil are doubled, then how will the magnetic field produced by it changes? Ans. Doubled Q.9 In which position the force on conductor is maximum when it is placed in uniform magnetic field? Ans. When conductor is Perpendicular to field Q-10 Suppose you are sitting in a room facing one of the wall. An electron beam moving horizontally from your back goes towards the wall in front you and is deflected to your left, what is the direction of magnetic field in the room? Ans. Vertically upward. Q-11 A current through a horizontal power line flows in north to south direction.What is the direction of magnetic field (i)at a point directly below it and (ii)at a point directly above it? Ans. (i) West to East (ii) East to West Q-12. Electric appliances like electric –press, toaster, fans etc are connected to electric mains through three-pin plug. Why ? Ans. Electric appliances are connected to three pin plug because heavy appliances require earth wire,so that in case of leakage of any current it goes to earth and user will not get shock. full study links
6 Comments
1. What is ore? [1]
Ans: An ore is a naturally occurring mineral from which one or more metals can be profitably extracted. 2. What is metallurgy? [1] Ans: Metallurgy is the science of extracting metals from their ores and purifying them. 3. Differentiate between metal and non–metals on the basis of any one physical property. [1] Ans: Metals are ductile. It is the property that allows the metals to be drawn into wires. Non metals are not ductile. 4. Give the reaction of magnesium with water. [1] Ans: Mg + 2H2O -----------> Mg(OH)2 + H2 5. What is alloy? [1] Ans: An alloy is a homogeneous mixture of a metal with another metal(s) or non–metal(s). 6. Define: (i) Concentration of ore (ii) Reduction [2] Ans: (i) Concentration of ore: It is the preliminary treatment of an ore in which impurities are removed. (ii) Reduction: The metal compound is reduced to get free metal 7. What is metallic luster? Why metals are useful for jewellery and decoration. [2] Ans: Metals have shiny appearance. This property is known as metallic luster.The shiny appearance makes the metals useful for jewellery and decoration 8. Explain conductivity in case of metals and non metals. [2] Ans: Metals are good conductor of heat and electricity. Gold is the best conductor followed by silver, copper and aluminum. Non–metals are generally bad conductors of heat and electricity. 9. Discuss the reaction of metals and non–metals with oxygen. [3] Ans: In general, metals form oxides on combining with oxygen. The water solutions of these oxide are alkaline or basic in nature and changes red litmus into blue. 2Mg + O2 ---------> 2MgO MgO + H2O-----> Mg (OH)2 Non metals too combine with oxygen to form oxides. However, such oxides are acidic in nature 10. Discuss the reaction of metals with water. [3] Ans: Sodium reacts violently with water. Magnesium reacts mildly with cold water but vigorously with hot water or steam. Mg + 2H2O -----------> Mg(OH)2 + H2 Zinc and iron react very mildly with steam, whereas copper, silver and nickel do not react with water.Non–metals also do not react with water. 11. What happens when iron nails are put in copper sulphate solution? [3] Ans: When iron nails are put in copper sulphate solution, the blue colour of the solution starts fading gradually. At the same time, iron nails get a shiny coating of red brown copper metal on their surface.This change takes place as iron displaces copper from copper sulphate. 12. What is electroplating? [5] Ans: Electroplating: Iron and steel are protected from corrosion by coating them with a layer of tin or chromium metals which are resistant to corrosion. This can be done by electroplating. A thin layer of tin deposited on the inner surface of iron containers makes them safe, for storing food. Chromium plating protects steel furniture, taps and bicycle handles from corrosion. Coating of chromium not only giveslonger life to the coated objects but also gives a good shining appearance to them. 13. Discuss some common uses of metals and non–metals? [5] Ans: Metals are strong, hard and rigid. So they are used in making machinery. The automobiles, the aeroplanes, the trains, satellites, industrial gadgets all use metals in large amounts. Iron is the most commonly used metal.
1. How is sound produced ?
Ans: Sound is produced by a vibrating body e.g. when a tightly stretched bond is plucked, it vibrates and produced sound. When it stops vibrating , it does not produced any sound . 2. How is sound produced by humans? Ans: In humans, the sounds is produced by the voice box or the larynx. Put your fingers on the throat and find a hard bump that seem to move when you swallow. This part of the body is known as the voice box. This is at the upper end of the wind pipe. Two vocal cords are stretched across the voice box or larynx in such a way that it leaves a narrow slit between them for the passage of air. When the lungs force air through the suit the vocal cords vibrate, producing sound. 3. why the voices of men, women and children are different. Ans: The vocal cords in men are about 20 mm long. In women these are about 15 mm shorter. Children have very short vocal cords. This is the reason why the voices of men, women and children are different. 4. What is oscillatory motion Ans: The to and fro motion of an object is known as vibration. This motion is also called oscillatory motion. The number of oscillations per second is called the frequency. It is expressed in hertz. Its symbol is Hz. Amplitude and frequency are important properties of any sound. 5. On what factor loudness of sound deepens on? Ans: Loudness is property of sound that distinguish loud sound from bass . The loudness of sound depends on its amplitude. It is proportional to the square of the amplitude of the vibration producing the sound. When the amplitude of vibration is large, the sound produced is loud. When the amplitude is small the sound produced is feeble. The loudness is expressed in a unit called decibel(dB). Above 80 dB the noise becomes physically painful. 6. What is pitch? Ans: It is the characteristics of sound distinguish shrillness and pitch of the sound. When the frequency of the vibration is higher, then the sound has a higher pitch. When the frequency of vibration is lower, then the sound has a low pitch. The frequency of the voice of a child is higher than that of an adult. The voice of a woman has higher frequency and is shriller than that of a man. 7. What is range of the frequency of audible sound ? Ans: The sounds of the frequencies less than about 20 vibrations per second (20 Hz) are called inaudible sounds or infrasonic. Such sound can not be detected by the human ear. The sound of frequencies higher than about 20,000 vibrations per second (20 kHz) are called the ultrasonic sound. For human ear, the range of audible frequencies is roughly from 20 to 20,000 Hz 8. Why are sound waves called mechanical waves? Ans: Sound waves force the medium particles to vibrate. because of the interaction of the particles present in that medium 9. What is SONAR? Ans: SONAR stands for Sound Navigation and Ranging and it works on the principle of reflection of sound waves. The SONAR technique is used to determine the depth of the sea and to locate under water hills, valleys, submarines, icebergs sunken ships etc. 10. What is the intensity of sound? Ans: The amount of sound energy passing each second through unit area is called the intensity of sound. 11. Define : (i) Reverberation of sound. (ii)Echo (iii) Time period (iv)Wavelength. (v) wave velocity (vi) compression. (vi) rarefaction Ans: (1)The persistence of sound due to repeated reflection and its gradual fading away is called reverberation of sound. (2) Echo is a repetition of sound due to the reflection of original sound by a large and hard obstacle. (3) Frequency is defined as the number of oscillations per second. The time taken by the wave for one complete oscillation of the density or pressure of the medium is called the time period, T. (4) The distance between two consecutive compressions or two consecutive rarefactions is called the wavelength. (5)The distance traveled by a wave in one second is called wave velocity. It depends upon the nature of the medium through which it passes. (6) The part or region of a longitudinal wave in which the density of the particles of the medium is higher than the normal density is known as compression. (7) The part or region of a longitudinal wave in which the density of the particles of the medium is lesser than the normal density is called a rarefaction. 13. What through and crest. The point of maximum positive displacement on a transverse wave is known as crest. The point of maximum negative displacement on a transverse wave is known as through.
|
Blog SeaRCH Link
All
Join Us For Update |