![]() (a) Electrostatic force on the first sphere, F = 0.2 NĬharge on this sphere, q 1 = 0.4 μC = 0.4 × 10 −6 CĬharge on the second sphere, q 2 = − 0.8 μC = − 0.8 × 10 −6 CĮlectrostatic force between the spheres is given by the relation, (a) What is the distance between the two spheres? (b) What is the force on the second sphere due to the first? The electrostatic force on a small sphere of charge 0.4 μC due to another small sphere of charge − 0.8 μC in air is 0.2 N. Hence, the force between the given charged particles will be Since the nature of the charges is the same i.e. Putting the values in equation (1), we get, F12 is the force on charge q1 caused by charge q2.ĭistance between the spheres, r = 30 cm = 0.3 m Since, both the charges are positive, thus, the nature of force will be repulsive. The formula used to find the force, F is given as, What is the force between two small charged spheres having charges of 2 × 10 −7 C and 3 × 10 −7 C placed 30 cm apart in air? NCERT Solutions for class-12 Physics Chapter 1 Electric Charges and Fields is prepared by our senior and renowned teachers of Physics Wallah primary focus while solving these questions of class-12 in NCERT textbook, also do read theory of this Chapter 1 Electric Charges and Fields while going before solving the NCERT questions. You can download and share NCERT Solutions of Class 12 Physics from Physics Wallah. The 7.80 kV value is the maximum emf obtained when θ = 90º and sin θ = 1.NCERT Solutions For Class 12 Physics chapter 1-Electric Charges And Fields The value obtained is greater than the 5 kV measured voltage for the shuttle experiment, since the actual orbital motion of the tether is not perpendicular to the Earth’s field. To find the magnitude of emf induced along the moving rod, we use Faraday’s law of induction without the sign: ![]() ![]() (Note that the script E symbol used in the equivalent circuit at the bottom of part (b) represents emf.) RHR-1 also indicates the same polarity for the rod. RHR-2 gives the current direction shown, and the polarity of the rod will drive such a current. Since the flux is increasing, the induced field is in the opposite direction, or out of the page. (b) Lenz’s law gives the directions of the induced field and current, and the polarity of the induced emf. The magnetic field B is into the page, perpendicular to the moving rod and rails and, hence, to the area enclosed by them. (a) A motional emf = Bℓ v is induced between the rails when this rod moves to the right in the uniform magnetic field. When flux changes, an emf is induced according to Faraday’s law of induction.įigure 1. Thus the magnetic flux enclosed by the rails, rod, and resistor is increasing. B is perpendicular to this area, and the area is increasing as the rod moves. Consider the area enclosed by the moving rod, rails, and resistor. The resistor could be anything from a light bulb to a voltmeter. The rails are stationary relative to B and are connected to a stationary resistor R. A rod is moved at a speed v along a pair of conducting rails separated by a distance ℓ in a uniform magnetic field B. Consider the situation shown in Figure 1. We will now see that the Hall effect is one aspect of the broader phenomenon of induction, and we will find that motional emf can be used as a power source. We saw that the Hall effect has applications, including measurements of B and v. Charges moving in a magnetic field experience the magnetic force F = qvB sin θ, which moves opposite charges in opposite directions and produces an em f = Bℓv. One situation where motional emf occurs is known as the Hall effect and has already been examined. In this section, we concentrate on motion in a magnetic field that is stationary relative to the Earth, producing what is loosely called motional emf. For example, a magnet moved toward a coil induces an emf, and a coil moved toward a magnet produces a similar emf. Motion is one of the major causes of induction. Calculate emf, force, magnetic field, and work due to the motion of an object in a magnetic field.Īs we have seen, any change in magnetic flux induces an emf opposing that change-a process known as induction.By the end of this section, you will be able to:
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