All STD 12 - Current electricity questions
Newest firstShowing 251–300 of 311 questions
- 251. Determine the charge on the capacitor in the following circuit ................ \(\mu C\)
2019 Medium - 252. Drift speed of electrons, when \(1.5\, A\) of current flows in a copper wire of cross section \(5\, mm^2\), is \(v\). If the electron density in copper is \(9 \times 10^{28}\, m^3\) the value of \(v\) in \(mm/s\) is close to (Take charge of electron to be \(= 1.6 \times 10^{-19}\, C\)) 2019 Medium
- 253. For the circuit shown, with \({R_1} = 1.0\,\Omega \), \({R_2} = 2.0\,\Omega \), \({E_1} = 2\,V\) and \({E_2} = {E_3} = 4\,V\), the potential difference between the points \(‘a’\) and \(‘b’\) is approximately (in \(V\))
2019 Medium - 254. In a conductor, if the number of conduction electrons per unit volume is \(8.5 \times 10^{28}\, m^{-3}\) and mean free time is \(25\,fs\) (femto second), its approximate resistivity is \(\left( {{m_e} = 9.1 \times {{10}^{ - 31}}\,kg} \right)\) 2019 Medium
- 255. In a meter bridge experiment, the circuit diagram and the corresponding observation table are shown in figure
Which of the readings is inconsistent ?\(Sl\). \(No\). \(R\, (\Omega )\) \(l\, (cm)\) \(1\). \(1000\) \(60\) \(2\). \(100\) \(13\) \(3\). \(10\) \(1.5\) \(4\). \(1\) \(1.0\) 
2019 Medium - 256. In a meter bridge, the wire of length \(1\, m\) has a nonuniform cross-section such that, the variation \(\frac{{dR}}{{d\ell }}\) of its resistance \(R\) with length \(\ell \) is \(\frac{{dR}}{{d\ell }} \propto \frac{1}{{\sqrt \ell }}\) Two equal resistances are connected as shown in the figure. The galvanometer has zero deflection when the jockey is at point \(P\). What is the length \(AP\) ? ................ \(m\)
2019 Hard - 257. In a Wheatstone bridge (see figure) Resistance \(P\) and \(Q\) are approximately equal. When \(R = 400\,\Omega ,\) the bridge is balanced. On interchanging \(P\) and \(Q,\) the value of \(R,\) for balance is \(405\,\Omega .\) The value of \(X\) is close to ................. \(ohm\)
2019 Medium - 258. In an experiment, the resistance of a material is plotted as a function of temperature (in some range). As shown in the figure, it is a straight line. One may conclude that:
2019 Hard - 259. In the circuit shown, a four wire potentiometer is made of a \(400\, cm\) long wire, which extends between \(A\) and \(B\). The resistance per unit length of the potentiometer wire is \(r = 0.01\, \Omega /cm\). If an ideal voltmeter is connected as shown with jockey \(J\) at \(50\, cm\) from end \(A\), the expected reading of the voltmeter will be: ............... \(V\)
2019 Medium - 260. In the circuit shown, the potential difference between \(A\) and \(B\) is ............. \(V\)
2019 Medium - 261. In the experimental setup of meter bridge shown in the figure, the null point is obtained at a distance of \(40\,cm\) from \(A\). If a \(10\,\Omega \) resistor is connected in series with \(R_1\), the null point shifts by \(10\,cm\). The resistance that should be connected in parallel with \(\left( {{R_1} + 10} \right)\,\Omega \) such that the null point shifts back to its initial position is .............. \(\Omega\)
2019 Hard - 262. In the figure shown, what is the current (in Ampere) drawn from the battery ? You are given \(R_1 = 15\,\Omega \)\(,R _2 = 10\,\Omega ,\)\( R_3 = 20\,\Omega ,\)\( R_4 = 5\,\Omega ,\)\(R_5 = 25\,\Omega ,\)\(R_6 = 30\,\Omega , \)\(E = 15\,V\)
2019 Medium - 263. In the given circuit, an ideal voltmeter connected across the \(10\,\Omega \) resistance reads \(2\, V\). The internal resistance \(r\), of each cell is ................... \(\Omega\)
2019 Medium - 264. In the given circuit diagram, the currents, \({I_1} = - \,0.3\,A,\,{I_4} = 0.8\,A\) and \({I_5} = 0.4\,A,\) are flowing as shown. The currents \(I_2,\,I_3\) and \(I_6,\) respectively are
2019 Medium - 265. In the given circuit the internal resistance of the \(18\,V\) cell is negligible. If \(R_1 = 400 \,\Omega ,\,R_3 = 100\,\Omega \) and \(R_4 = 500\,\Omega \) and the reading of an ideal voltmeter across \(R_4\) is \(5\,V,\) then the value of \(R_2\) will be ........... \(\Omega\)
2019 Medium - 266. One \(kg\) of water, at \(20\,^oC\), is heated in an electric kettle whose heating element has a mean (temperature averaged) resistance of \(20\, \Omega \). The rms voltage in the mains is \(200\, V\). Ignoring heat loss from the kettle, time taken for water to evaporate fully, is close to.......... \(\min\) [Specific heat of water \(= 4200\, J/kg\, ^oC\)), Latent heat of water \(= 2260\, k\,J/kg\)] 2019 Hard
- 267. Space between two concentric conducting spheres of radii \(a\) and \(b (b > a)\) is filled with \(a\) medium of resistivity \(\rho \). The resistance between the two spheres will be 2019 Hard
- 268. The actual value of resistance \(R\), shown in the figure is \(30\,\Omega \). This is measured in an experiment as shown using the standard formula \(R = \frac{V}{I}\) where \(V\) and \(I\) are the readings of the voltmeter and ammeter, respectively. If the measured value of \(R\) is \(5\%\) less, then the internal resistance of the voltmeter is ................. \(\Omega\)
2019 Medium - 269. The charge on a capacitor plate in a circuit, as a function of time, is shown in the figure What is the value of current at \(t = 4\,s\) ? ............... \(\mu A\)
2019 Easy - 270. The galvanometer deflection, when key \(K_1\) is closed but \(K_2\) is open, equals \(\theta_0\) (see figure). On closing \(K_2\) also and adjusting \(R_2\) to \(5\,\Omega \) , the deflection in galvanometer becomes \(\frac{{\theta _0}}{5}\). The resistance of the galvanometer is, then, given by [Neglect the internal resistance of battery]: .................. \(\Omega\)
2019 Hard - 271. The resistance of the meter bridge \(AB\) in given figure is \(4\,\Omega \). With a cell of emf \(\varepsilon \, = 0.5\,\,V\) and rheostat resistance \(R_h = 2\,\Omega \) the null point is obtained at some point \(J.\) When the cell is replaced by another one of emf \(\varepsilon \, = {\varepsilon _2}\) the same null point \(J\) is found for \(R_h = 6\,\Omega .\) The \(emf\) \({\varepsilon _2}\) is ................. \(V\)
2019 Hard - 272. The resistive network shown below is connected to a \(D.C.\) source of \(16\, V\). The power consumed by the network is \(4\, Watt\). The value of \(R\) is ............. \(\Omega\)
2019 Medium - 273. The Wheatstone bridge shown in Fig. here, gets balanced when the carbon resistor used as \(R_1\) has the colour code (Orange, Red, Brown). The resistors \(R_2\) and \(R_4\) are \(80\, \Omega \) and \(40\,\Omega \), respectively. Assuming that the colour code for the carbon resistors gives their accurate values, the colour code for the carbon resistor, used as \(R_3\) would be
2019 Hard - 274. To verify Ohm's law, a student connects the voltmeter across the battery as, shown in the figure. The measured voltage is plotted as a function of the current, and the following graph is obtained If \(V_0\) is almost zero, identify the correct statement
2019 Medium - 275. Two electric bulbs, rated at \((25\, W, 220\, V)\) and \((100\, W, 220\, V)\), are connected in series acroos a \(220\, V\) voltage source. If the \(25\, W\) and \(100\, W\) bulbs draw powers \(P_1\) and \(P_2\) respectively, then 2019 Hard
- 276. Two equal resistances when connected in series to a battery, consume electric power of \(60\,W.\) If these resistances are now connected in parallel combination to the same battery, the electric power consumed will be .............. \(W\) 2019 Medium
- 277. When the switch \(S\), in the circuit shown, is closed, then the value of current \(i\) will be ................. \(A\)
2019 Medium - 278. A constant voltage is applied between two ends of a metallic wire. If the length is halved and the radius of the wire is doubled, the rate of heat developed in the wire will be 2018 Hard
- 279. A copper rod of cross-sectional area \(A\) carries a uniform current \(I\) through it. At temperature \(T\), if the volume charge density of the rod is \(\rho \), how long will the charges take to travel a distance \(d\) ? 2018 Medium
- 280. A heating element has a resistance of \(100\,\Omega \) at room temperature. When it is connected to a supply of \(220\,V,\) a steady current of \(2\,A\) passes in it and temperature is \(500\,^oC\) more than room temperature. What is the temperature coefficient resistance of the heating element? 2018 Hard
- 281. In a meter bridge, as shown in the figure, it is given that resistance \(Y=12.5\, \Omega \) and that the balance is obtained at a distance \(39.5\, cm\) from end \(A\) (by jockey \(J\)) . After interchanging the resistances \(X\) and \(Y\), a new balance point is found at a distance \(l_2\) from end \(A\). What are the values of \(X\)and \(l_2\) ?
2018 Hard - 282. In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across \(52\ cm\) of the potentiometer wire. If the cell is shunted by a resistance of \( 5\,\Omega\), a balance is found when the cell is connected across \(40\ cm\) of the wire. Find the internal resistance of the cell ........... \(\Omega\) 2018 Medium
- 283. In the given circuit all resistances are of value \(R\,ohm\) each. The equivalent resistance between \(A\) and \(B\) is
2018 Hard - 284. On interchanging the resistances, the balance point of a meter bridge shifts to the left by \(10\ cm\). The resistance of their series combination is \(1\ k\Omega\). How much was the resistance on the left slot before interchanging the resistances? .................. \(\Omega\) 2018 Hard
- 285. Two batteries with e.m.f \(12\ V\) and \(13\ V\) are connected in parallel across a load resistor of \(10\,\Omega\) . The internal resistances of the two batteries are \(1\,\Omega\) and \(2\,\Omega\) respectively. The voltage across the load lies between 2018 Medium
- 286. A \(9\, V\) battery with internal resistance of \(0.5\,\Omega \) is connected across an infinite network as shown in the figure. All ammeters \(A_1 , A_2, A_3\) and voltmeter \(V\) are ideal. Choose correct statement
2017 Hard - 287. A potentiometer \(PQ\) is set up to compare two resistances as shown in the figure. The ameter \(A\) in the circuit reads \(1.0\, A\) when two way key \(K_3\) is open. The balance point is at a length \(l_1\, cm\) from \(P\) when two way key \(K_3\) is plugged in between \(2\) and \(1\) , while the balance point is at a length \(l_2\, cm\) from \(P\) when key \(K_3\) is plugged in between \(3\) and \(1\) . The ratio of two resistances \(\frac{{{R_1}}}{{{R_2}}}\) is found to be
2017 Medium - 288. A uniform wire of length \(l\) and radius \(r\) has a resistance of \(100\, \Omega \). It is recast into a wire of radius \(\frac{r}{2}\). The resistance of new wire will be ............... \(\Omega\) 2017 Hard
- 289. In a meter bridge experiment resistances are connected as shown in the figure. Initially resistance \(P\, = 4\,\Omega \) and the neutral point \(N\) is at \(60\,cm\) from \(A\). Now an unknown resistance \(R\) is connected in series to \(P\) and the new position of the neutral point is at \(80\,cm\) from \(A\) . The value of unknown resistance \(R\) is
2017 Hard - 290. In the below circuit the current in each resistance is
2017 Easy - 291. In the given circuit diagram when the current reaches steady state in the circuit, the charge on the capacitor of capacitance \(C\) will be
2017 Medium - 292. The figure shows three circuits \(I, II\) and \(III\) which are connected to a \(3\,V\) battery. If the powers dissipated by the configurations \(I, II\) and \(III\) are \(P_1 , P_2\) and \(P_3\) respectively, then
2017 Hard - 293. Which of the following statements is false? 2017 Easy
- 294. In the circuit shown, the resistance \(r\) is a variable resistance. If for \(r = fR,\) the heat generation in \(r\) is maximum then the value of \(f\) is
2016 Hard - 295. In the following \('I'\) refers to current and other symbols have their usual meaning, Choose the option that corresponds to the dimensions of electrical conductivity 2016 Medium
- 296. The resistance of an electrical toaster has a temperature dependence given by \(R\left( T \right) = {R_0}\left[ {1 + \alpha \left( {T - {T_0}} \right)} \right]\) in its range of operation. At \({T_0} = 300\,K,R = 100\,\Omega \) and at \(T = 500\,K,\,R = 120\,\Omega \). The toaster is connected to a voltage source at \(200\, V\) and its temperature is raised at a constant rate from \(300\) to \(500\, K\) in \(30\, s\). The total work done in raising the temperature is 2016 Hard
- 297. A \(10\,V\) battery with internal resistance \(1\,\Omega \) and a \(15\,V\) battery with internal resistance \(0.6\,\Omega \) are connected in parallel to a voltmeter (see figure). The reading in the voltmeter will be close to ................ \(V\)
2015 Hard - 298. In the electric network shown, when no current flows through the \(4\, \Omega \) resistor in the arm \(EB\), the potential difference between the points \(A\) and \(D\) will be ............... \(V\)
2015 Hard - 299. When \(5\ V\) potential difference is applied across a wire of length \(0.1\ m\), the drift speed of electrons is \(2.5 \times 10^{-4}\) \(ms^{-1}\) . If the electron density in the wire is \(8 \times 10^{28}\) \(m^{-3}\) the resistivity of the material is close to 2015 Medium
- 300. A \(d.c.\) main supply of \(e.m.f.\, 220\, V\) is connected across a storage battery of \(e.m.f.\, 200\, V\) through a resistance of \(1\,\Omega \). The battery terminals are connected to an external resistance \('R'\) . The minimum value of \('R'\), so that a current passes through the battery to charge it is ............... \(\Omega\) 2014 Hard
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