Unit 11 Electricity and Magnetism PDF

# 11. Electricity and Magnetism ## Multiple Choice Questions 1. Choose the correct options for the following questions: **(a) Which ac source is there in the table?** * Driesel * **Solar panel** * Dynamo * Voltaic cell **(b) Which scientist has discovered the m...

# 11. Electricity and Magnetism ## Multiple Choice Questions 1. Choose the correct options for the following questions: **(a) Which ac source is there in the table?** * Driesel * **Solar panel** * Dynamo * Voltaic cell **(b) Which scientist has discovered the magnetic effect of electric current?** * Michael Faraday * **Hans Christian Oersted** * John Ambrose Fleming * James Clerk Maxwell **(c) What should be the direction of the magnetic field in the case of electric current flowing through a conductor straight wire?** * The direction of rotation of the clock needle is reversed. * **The hands of a clock rotate in the same direction.** * Electric current has a perpendicular direction. * The electric current is in the opposite direction. **(d) Which statement about the electric source shown in the diagram is correct?** * The value of the electric current produced by A weight is constant. * **B is the frequency of the electric current produced by the bat.** * The electric current produced by a bulb increases and decreases. * The direction of the electric current produced by the weight changes continuously. **(e) On what principle is the transformer based?** * Electromagnetic induction * **Mutual induction** * Motor bearing * Electromagnetic effect **(f) What is the transformer formula?** * (Come) * (1) * **(E)** ## Write the Difference. **(a) AC and DC** **AC:** * If the current is considered to be flowing and the direction changes for a certain period of time, then the current is called AC current. * Sources of AC current are dynamo generator etc. * It's frequency is like 50 Hz. * This current can be transmitted over long distances. **DC:** * If the current flows only in a certain direction then the current is called DC current. * Sources of DC current are solar panels, dry cells etc. * It is repeated. * This current is being broadcasted remotely. **(b) dynamo and generator** **Dynamo:** * Any good means of transportation like a bicycle which has a support weight and a device for converting mechanical power into electrical power is called dynamo. * Dynamobat can extract small amounts of electricity. **Generator:** * Any object like steam, water etc. which converts mechanical power into electrical power is called a generator. * A large amount of electricity can be extracted from the generator. **(c) motor and generator** **Motor:** * It converts electrical power into mechanical power. * It works on the principle of motor bearing. **Generator:** * It converts mechanical power into electrical power. * It works on the basis of Faraday's laws of electromagnetic induction. **(d) Step up transformer and step down transformer** **Step up transformer:** * The transformer used to increase the voltage of alternating current should be a state up transformer. * The number of discharges of the secondary coil is greater than the number of discharges of the primary coil. **Step down transformer:** * The transformer used to reduce the voltage of alternating current is a step down transformer. * The Funkako number of the secondary coil is less than the Funkako number of the primary coil. ## Write Reason: **(a) Electric circuit drawn from a solar panel, ceiling fan rotating.** * Because the AC motor is connected to the ceiling fan and the electricity drawn from the solar panel is DC, due to which the AC motor does not work, as a result the ceiling fan rotates. **(b) Keep a magnetic compass near the circuit in which electric current is flowing and move its needle.** * Because when electric current flows through any wire, a magnetic field is created around the said wire, due to which a magnetic compass is placed around it and its needle moves. **(c) In the electric bell, electromagnetism is used.** * By using a permanent magnet in an electric bell, the attraction brought by the said magnet to the armature keeps the bell from ringing and hence it is not possible to ring the bell, whereas if an electromagnet is used then the process of opening and closing of the electric circuit continues continuously due to which the bell can be rung continuously. **(d) The number of primary terminals and secondary terminals of the transformer is not the same.** * The output voltage can be increased or decreased only depending on the number of primary windings and secondary windings of the transformer. The number of primary and secondary windings is equal in the transformer. The voltage change cannot be calculated, hence the number of primary and secondary windings in the transformer is not equal. **(e) The core of the transformer is laminated.** * When current flows in the coil of the transformer, it causes unnecessary current (eddy current) to flow in the coil, which causes the transformer to wear out more when used for a long time. Therefore, to reduce the loss of input power, as well as to save or reduce the loss of the transformer coil, its core lamination is done. **(f) Transformer is used in mobile charger.** * Because the voltage required to charge the mobile is around 5V, if there is 240V current in our power supply, then a step down transformer is connected to the mobile charger to draw 240V. ## Write the Answers to the Questions Given Below. **(a) Write the meaning of saying that the frequency of AC used in our country is 50 Hz.** * This means that the rotor of the AC generating motor gets extinguished and makes 50 complete revolutions in one second. This means that the AC used in our country changes direction every 100 seconds. **(b) Draw the graph of direct and alternating current.** * [This is a request to generate an image, which is outside the scope of this tool.] **(c) Draw a diagram of the magnetic field around a straight wire carrying current and the solenoid.** * [This is a request to generate an image, which is outside the scope of this tool.] **(d) Explain the following rule:** * **Maxwell's right-hand rule to show the direction of the magnetic field formed due to the effect of electric current on a straight wire.** * If a wire is being affected by an electric current, as seen in Figure 11.12, the old man holding his right hand with a clenched fist is imagined to show the direction of the current flow and the hand's unclenching indicates the direction of the magnetic force line. * Maxwell's right hand rule to find direction to the magnetic force line, the surrounding of the solenoid, the old Aula's law. * If you clench your fist in the direction of current flow in the right hand solenoid, the magnetic field formed around the right hand solenoid will show the north pole. **(e) What is the magnetic effect of electric current?** * When an electric current flows through a wire, the magnetic field created around the said wire is called magnetic effect. **(f) Write the definition of magnetic flux.** * The area of a surface outside a magnetic field is known as the total number of magnetic force lines, that is, the magnetic field can be measured by the area of a surface outside a magnetic field. Its sole owner is Weber. **(g) Wash the flame, use cardboard and a conducting straight wire. Explain how the magnetic field around a straight wire carrying current can be determined.** * After leaving a straight wire of cardboard and connecting it to the electrical circuit, sprinkle the flame on the cardboard very finely and then sweep the circuit and slowly gaze at it with the tip of the cardboard. **(h) Draw a diagram of the magnetic field around a straight wire carrying a current carrying electric current.** * [This is a request to generate an image, which is outside the scope of this tool.] **(i) What is a solenoid? Draw a picture of the magnetic field surrounding the solenoid.** * Lamcho coil made of insulated wire spring shaped is called solenoid. * [This is a request to generate an image, which is outside the scope of this tool.] **(j) There is no question.** **(T) There is no question.** **(1) Write the utility of solenbide duodenum.** **(d) Which effect is demonstrated in the given picture?** * In the given picture motor bearing is presented. **(n) A simple electric motor is shown in the picture of a cell, coil, paper clip, dry cell and permanent magnet. Describe the working process of the said motor on the basis of motor bearing.** * When there is an electric current in the coil, magnetism is generated due to the magnetic effect of the electric current. The coil rotates due to the interaction between the magnetization of the coil and the magnetic field generated by the permanent magnet. **(n) What is electromagnetic induction?** * When the magnetic flux changes related to a closed electric circuit, electromotive force i.e. voltage is produced in the said circuit. The action should be electromagnetic induction. **(t) Study the given picture and write that the plane is in the same state.** **(a) Bar magnet entering inside the extension solenoid.** * The needle of the Galvanometer starts moving. **(B) Bar magnet is inserted into the self-contained coil at high speed.** * The needle of the Galvanometer should be moved rapidly. **(e) Static current inside the bar magnet solenoid.** * The needle of the Galvanometer stops moving. **(e) Bar magnetized solenoid outside sharp point** * The needle moves at high speed in the opposite direction. **(Q) Write Faradaco's law related to electromagnetic induction.** * When there is relative motion between a conductor and a magnet, an emf is produced in the conductor. The magnitude of the said emf is proportional to the rate of change of the magnetic flux associated with the conductor. **(d) A bulb connected to a dynamo is connected to a single-nasal lamp, it glows at some times, and at some times it becomes sweet, and when the cycle comes to a stable state, insert the bulb. Give reasons for this type of observation based on the working process of a dynamo.** * The amount of electric current generated by the dynamo coil's induced voltage is equal to the change in magnetic flux. The rate of change of magnetic flux is proportional to the speed of the cycle, hence the brightness of the rapidly rotating bulb increases and when the cycle comes to steady state, the rate of change of magnetic effect is zero due to which no voltage is produced, hence in this situation the bulb is extinguished. **(d) Write any two ways in which the amount of electricity produced by a dynamo weight can be increased.** * Increase the number of funka having quailma * Increase the strength of the magnetic field * By reducing the distance between the magnet and the coil **(P) What is a transformer?** * The equipment used to increase and decrease alternating voltage is called transformer. **(f) Write the type of transformers X and Y shown in the figure.** * J= step up transformer * K= step down transformer **(B) Draw the picture of step up transformer and step down transformer and write the utility of each 2/2 watt.** **Step up transformer** 1. Transmission Line 2. X-ray machine **Step down transformer** 1. Mobile Charger 2. Rectifiers ## Mathematical problem **(a) If 220 V power supply is required to charge the laptop, calculate the number of primary fans of the charger and transformer and the number of secondary fans.** **Solution** According to the question, * Primary Voltage (Vp) = 220V * Secondary voltage (Vs) = 20V (Laptop voltage) * Primary Funka (Np) = 500 * Secondary function (Ns) to be calculated According to transformer formula, * Primary current (Np) = Primary voltage (Vp). * Secondary current (Ns) = Secondary voltage (VS) * Or, 550 = 220 * Ns = 20 * or 550\*20 = Ns\*220 * or Ns = 11000/220 * or Ns = 50 Therefore the secondary funkako number is 50. **(b) The efficiency of the transformer used in a microwave oven is 10 times that of the primary coil. What is the secondary voltage when a 230 V potential difference circuit is connected to the above microwave oven?** According to the question, * Primary Voltage (Vp) = 230V * Secondary voltage (Vs) = ? * Primary function (Np) = x (say) * Secondary function (Ns) = 10x According to transformer formula, * Primary current (Np) = Primary voltage (Vp). * Secondary current (Ns) = Secondary voltage (VS) * Or, x = 230 * 10x = Vs * Or, 1 = 230 * 10 = Vs * Or, Vs = 2300V Hence the secondary voltage is 2300V. **(c) If the ratio of primary winding and secondary winding of a transformer is 22:1, then calculate the output voltage obtained by connecting the circuit with a 220 V potential difference using an adapter.** According to the question, * Primary Voltage (Vp) = 220V * Secondary voltage (Vs) = ? * Primary Funka (Np) = 22x (Assume) * Secondary function (Ns) = x According to transformer formula, * Primary current (Np) = Primary voltage (VP) * Secondary current (Ns) = Secondary voltage (vs) * Or, 22x = 220 * X=VS * Or, 22 = 220 * 1=Vs * Or, Vs = 220 * 22 Hence the secondary voltage is 10V.