All STD 12 - Moving charges and magnetism questions
Newest firstShowing 201–244 of 244 questions
- 201. A thin ring of \(10\, cm\) radius carries a uniformly distributed charge. The ring rotates at a constant angular speed of \(40\,\pi \,rad\,{s^{ - 1}}\) about its axis, perpendicular to its plane. If the magnetic field at its centre is \(3.8 \times {10^{ - 9}}\,T\), then the charge carried by the ring is close to \(\left( {{\mu _0} = 4\pi \times {{10}^{ - 7}}\,N/{A^2}} \right)\) 2019 Medium
- 202. An electron, moving along the \(x-\) axis with an initial energy of \(100\, eV\), enters a region of magnetic field \(\vec B = (1.5\times10^{-3}T)\hat k\) at \(S\) (See figure). The field extends between \(x = 0\) and \(x = 2\, cm\). The electron is detected at the point \(Q\) on a screen placed \(8\, cm\) away from the point \(S\). The distance \(d\) between \(P\) and \(Q\) (on the screen) is :......\(cm\) (electron's charge \(= 1.6\times10^{-19}\, C\), mass of electron \(= 9.1\times10^{-31}\, kg\))
2019 Hard - 203. An infinitely long current carrying wire and a small current carrying loop are in the plane of the paper as shown. the radius of the loop is \(a\) and distance of its centre from the wire is \(d (d >> a)\). If the loop applies a force \(F\) on the wire then
2019 Hard - 204. An insulating thin rod of length \(l\) has a linear charge density \(\rho \left( x \right) = {\rho _0}\,\frac{x}{l}\) on it. The rod is rotated about an axis passing through the origin \((x = 0)\) and perpendicular to the rod. If the rod makes \(n\) rotations per second, then the time averaged magnetic moment of the rod is 2019 Hard
- 205. As shown in the figure, two infinitely long, identical wires are bent by \(90^o\) and placed in such a way that the segments \(LP\) and \(QM\) are along the \(x-\) axis, while segments \(PS\) and \(QN\) are parallel to the \(y-\) axis. If \(OP = OQ = 4\, cm\), and the magnitude of the magnetic field at \(O\) is \(10^{-4}\, T\), and the two wires carry equal current (see figure), the magnitude of the current in each wire and the direction of the magnetic field at \(O\) will be \((\mu_ 0 = 4\pi \times10^{-7}\, NA^{-2})\)
2019 Hard - 206. Find the magnetic field at point \(P\) due to a straight line segment \(AB\) of length \(6\, cm\) carrying a current of \(5\, A\). (See figure) \((\mu _0 = 4p\times10^{-7}\, N-A^{-2})\)
2019 Hard - 207. In an experiment, electrons are accelerated, from rest, by applying, a voltage of \(500 \,V.\) Calculate the radius of the path if a magnetic field \(100\,mT\) is then applied. [Charge of the electron \(= 1.6 \times 10^{-19}\,C\) Mass of the electron \(= 9.1 \times 10^{-31}\,kg\) ] 2019 Medium
- 208. One of the two identical conducing wires of length \(L\) is bent in the form of a circular loop and the other one into a circular coil of \(N\) identical turns. If the same current is passed in both, the ratio of the magnetic field at the central of the loop \((B_L)\) to that at the centre of the coil \((B_C),\); \(.\,\frac {B_L}{B_C}\) will be 2019 Medium
- 209. The magnitude of the magnetic field at the centre of an equilateral triangular loop of side \(1\,m\) which is carrying a current of \(10\,A\) is:......\(\mu T\) [Take \(\mu _0 = 4\pi \times 10^{-7}\,NA^{-2}\)] 2019 Medium
- 210. The region between \(y = 0\) and \(y = d\) contains a magnetic field \(\vec B = B\hat z\) A particle of mass \(m\) and charge \(q\) enters the region with a velocity \(\vec v = v\hat i\). If \(d = \frac{{mv}}{{2qB}}\) , the acceleration of the charged particle at the point of its emergence at the other side is 2019 Hard
- 211. The resistance of a galvanometer is \(50\, ohm\) and the maximum current which can be passed through it is \(0.002\, A\). What resistance must be connected to it in order to convert it into an ammeter of range \(0 -0.5\, A\) ?....\(ohm\) 2019 Medium
- 212. Two very long, straight and insulated wires are kept at \(90^o\) angle from each other In \(xy -\) plane as shown in the figure. These wires carry current of equal magnitude \(I\), whose directions are shown in the figure. The net magnetic field at point \(P\) will be
2019 Medium - 213. Two wires \(A\) and \(B\) are carrying currents \(I_1\) and \(I_2\) as shown in the figure. The separation between them is \(d\). A third wire \(C\) carrying a current \(I\) is to be kept parallel to them at a distance \(x\) from \(A\) such that the net force acting on it is zero. The possible values of \(x\) are
2019 Medium - 214. A charge \(q\) is spread uniformly over an insulated loop of radius \(r\) . If it is rotated with an angular velocity \(\omega \) with respect to normal axis then the magnetic moment of the loop is 2018 Medium
- 215. A current of \(1\,A\) is flowing on the sides of an equilateral triangle of side \(4.5\times10^{-2}\,m\) . The magnetic field at the centre of the triangle will be 2018 Hard
- 216. A galvanometer with its coil resistance \(25\,\Omega \) requires a current of \(1\,mA\) for its full deflection. In order to construct an ammeter to read up to a current of \(2\,A,\) the approximate value of the shunt resistance should be 2018 Hard
- 217. A Helmholtz coil has pair of loops, each with \(N\) turns and radius \(R\). They are placed coaxially at distance \(R\) and the same current \(I\) flows through the loops in the same direction. The magnitude of magnetic field at \(P\), midway between the centres \(A\) and \(C\), is given by (Refer to figure)
2018 Hard - 218. An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii \(r_e,r_p\) and \({r_\alpha }\) respectively in a uniform magnetic field \(B\). The relation between \(r_e,r_p\) and \(\;{r_\alpha }\) is 2018 Medium
- 219. In a circuit for finding the resistance of a galvanometer by half deflection method, a \(6\,V\) battery and a high resistance of \(11\,k\Omega \) are used. The figure of merit of the galvanometer \(60\,\mu A/\) division. In the absence of shunt resistance, the galvanometer produces a deflection of \(\theta = 9\) divisions when current flows in the circuit. The value of the shunt resistance that can cause the deflection of \(\theta /2 ,\) is closest to .................. \(\Omega\) 2018 Hard
- 220. The dipole moment of a circular loop carrying a current \(I\), is \(m\) and the magnetic field at the centre of the loop is \(B_1\) . When the dipole moment is doubled by keeping the current constant, the magnetic field at the centre of the loop is \(B_2\) . The ratio \(\frac{{{B_1}}}{{{B_2}}}\) is 2018 Medium
- 221. A negative test charge is moving near a long straight wire carrying a current. The force acting on the test charge is parallel to the direction of the current. The motion of the charge is 2017 Medium
- 222. In a certain region static electric and magnetic fields exist. The magnetic field is given by \(\vec B = {B_0}\left( {\hat i + 2\hat j - 4\hat k} \right)\). If a test charge moving with a velocity \(\vec v = {v_0}\left( {3\hat i - \hat j + 2\hat k} \right)\) experiences no force in that region, then the electric field in the region, in \(SI\, units\), is 2017 Medium
- 223. When a current of \(5\ mA\) is passed through a galvanometer having a coil of resistance \(15\ \Omega\), it shows full scale deflection. The value of the resistance to be put in series with the galvanometer to convert it into to voltmeter of range \(0 - 10\ V\) is 2017 Medium
- 224. A \(50\,\Omega \) resistance is connected to a battery of \(5\,V\). A galvanometer of resistance \(100\, \Omega \) is to be used as an ammeter to measure current through the resistance, for this a resistance \(r_s\) is connected to the galvanometer. Which of the following connections should be employed if the measured current is within \(1\% \) of the current without the ammeter in the circuit ? 2016 Hard
- 225. A galvanometer has a \(50\) \(division\) scale. Battery has no internal resistance. It is found that there is deflection of \(40\) \(divisions\) when \(R = 2400\,\Omega \). Deflection becomes \(20\) \(divisions\) when resistance taken from resistance box is \(4900\,\Omega \) . Then we can conclude
2016 Hard - 226. A galvanometer having a coil resistance of \(100\ \Omega\). gives a full scale deflection, when a currect of \(I\ mA\) is passed through it. The value of the resistance, which can convert this galvanometer into ammeter giving a full scale deflection for a current of \(10\ A\), is :......\(Ω\) 2016 Medium
- 227. Consider a thin metallic sheet perpendicular to the plane of the paper moving with speed \('v'\) in a uniform magnetic field \(B\) going into the plane of the paper (See figure). If charge densities \({\sigma _1}\) and \({\sigma _2}\) are induced on the left and right surfaces, respectively, of the sheet then (ignore fringe effects)
2016 Medium - 228. To know the resistance \(G\) of a galvanometer by half deflection method, a battery of \(emf\, V_E\) and resistance \(R\) is used to deflect the galvanometer by angle \(\theta \). If a shunt of resistance \(S\) is needed to get half deflection then \(G, R\) and \(S\) related by the equation 2016 Hard
- 229. A proton (mass \(m\) ) accelerated by a potential difference \(V\) flies through a uniform transverse magnetic field \(B.\) The field occupies a region of space by width \('d'\). If \(\alpha \) be the angle of deviation of proton from initial direction of motion (see figure), the value of \(sin\,\alpha \) will be
2015 Hard - 230. A wire carrying current \(I\) is tied between points \(P\) and \(Q\) and is in the shape of a circular arc of radius \(R\) due to a uniform magnetic field \(B\) (perpendicular to the plane of the paper, shown by \(\times \times \times \)) in the vicinity of the wire. If the wire subtends an angle \(2\theta_0\) at the centre of the circle (of which it forms an arc) then the tension in the wire is
2015 Medium - 231. Two coaxial solenoids of different radii carry current \(I\) in the same direction. Let \(\;{\overrightarrow {\;F} _1}\) be the magnetic force on the inner solenoid due to the outer one and \(\;{\overrightarrow {\;F} _2}\) be the magnetic force on the outer solenoid due to the inner one. Then 2015 Medium
- 232. Two long current carrying thin wires, both with current \(I\), are held by insulating threads oflength \(L\) and are in equilibrium as shown in the figure, with threads making an angle '\(\theta\)' with the vertical. If wires have mass \(\lambda\) per unit length then the value of \(l\) is
(\(g =\) gravitational acceleration)
2015 Hard - 233. A conductor lies along the \(z-\)axis \(a\) \(-1.5\)\( \le Z < 1.5\,m\) carries a fixed current of \(10.0\ A\) in \( - {\hat a_z}\) direction (see figure). For a field \(\vec B\) \(=\) \(3.0 \times 10^{-4}\) \(e^{-0.2x}\) \({\hat a_y}\,T\) find the power required to move the conductor at constant speed to \(x = 2.0\ m, y = 0\ m\) in \(5 \times 10^{-3}\ s\). Assume parallel motion along the \(x-\)axis........\( W\)
2014 Hard - 234. A positive charge \('q'\) of mass \('m'\) is moving along the \(+ x\) axis. We wish to apply a uniform magnetic field \(B\) for time \(\Delta t\) so that the charge reverses its direction crossing the \(y\) axis at a distance \(d.\) Then 2014 Hard
- 235. Consider two thin identical conducting wires covered with very thin insulating material. One of the wires is bent into a loop and produces magnetic field \(B_1,\) at its centre when a current \(I\) passes through it.The second wire is bent into a coil with three identical loops adjacent to each other and produces magnetic field \(B_2\) at the centre of the loops when current \(I/3\) passes through it. The ratio \(B_1 : B_2\) is 2014 Hard
- 236. In the circuit diagrams \((A, B, C\) and \(D\)) shown below, \(R\) is a high resistance and \(S\) is a resistance of the order of galvanometer resistance \(G\). The correct circuit, corresponding to the half deflection method for finding the resistance and figure of merit of the galvanometer, is the circuit labelled as
2014 Hard - 237. Three straight parallel current carrying conductors are shown in the figure. The force experienced by the middle conductor of length \(25\,cm\) is
2014 Hard - 238. A current \(i\) is flowing in a straight conductor of length \(L.\) The magnetic induction at a point on its axis at a distance \(\frac {L}{4}\) from its centre will be 2013 Medium
- 239. A parallel plate capacitor of area \(60\, cm^2\) and separation \(3\, mm\) is charged initially to \(90\, \mu C\). If the medium between the plate gets slightly conducting and the plate loses the charge initially at the rate of \(2.5\times10^{-8}\, C/s\), then what is the magnetic field between the plates ? 2013 Medium
- 240. A particle of charge \(16\times10^{-16}\, C\) moving with velocity \(10\, ms^{-1}\) along \(x-\) axis enters a region where magnetic field of induction \(\vec B\) is along the \(y-\) axis and an electric field of magnitude \(10^4\, Vm^{-1}\) is along the negative \(z-\) axis. If the charged particle continues moving along \(x-\) axis, the magnitude of \(\vec B\) is 2013 Medium
- 241. A shunt of resistance \(1\,\Omega \) is connected across a galvanometer of \(120\,\Omega \) resistance. A current of \(5.5\, ampere\) gives full scale deflection in the galvanometer. The current that will give full scale deflection in the absence of the shunt is nearly ............... \(ampere\) 2013 Medium
- 242. Bob of a simple pendulum of length \(l\) is made of iron . The pendulum is oscillating over a horizontal coil carrying direct current. If the time period of the pendulum is \(T\) then 2013 Medium
- 243. One of the two small circular coils, (none of them having any self- inductance) is suspended with a \(V-\) shaped copper wire, with plane horizontal. The other coil is placed just below the first one with plane horizontal. Both the coils are connected in series with a \(dc\) supply. The coils are found to attract each other with a force. Which one of the following statements is incorrect ? 2013 Hard
- 244. This questions has Statement \(I\) and Statement \(II\) Of the four choices given after the Statements, choose the one that best describes into two Statements.
Statement\(-I\) : Higher the range, greater is the resistance of ameter.
Statement\(-II\) : To increase the range of ammeter, additional shunt needs to be used across it. 2013 Easy
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