All questions
- What is a thermistor? A heat-sensitive resistor whose resistance varies appreciably with temperature is known as a thermistor. 1
- A wire is carrying current. Is it charged? Give reason. No. Current is the flow’ of free electrons in the conductor. At any instant, the number of electrons leaving the wire and that flowing from... 1
- Give the colour code of 240 MΩ of 10% 240 MΩ = 240 x 10⁶ Ω = 24 x 10⁷ Ω ∴ colour code for 2 → Red colour code for 4 → Yellow colour code for 2 → Violet colour code for 2 → Silver... 1
- Two students X and Y perform an experiment on a potentiometer separately using the circuit diagram shown here (i) When the value of resistance R is increased, then the current from the driver cell decreases in the potentiometer, the potential gradien... 1
- 12 cells, each having the same emf are connected in series and are kept in a closed box. A reverse cell decreases the emf by 2 ε. Let ‘n’ cells be in opposition, then in the first connection 12ε – 2nε + 2ε = 3R 14ε – 2 nε = 3R …... 1
- One section AB of a circuit absorbs 53.0 W of power when a current i = 1.20 A passes through it in the direction shown. Let ‘r’ be the internal resistance of C. The power relation is i²(R + r) = 53.0 But R = 19.0 and i = 1.20 A r = frac53.0(1.2)² – 19.0 = 17.8... 1
- Two charges 5 x 10-8 C and – 3 x 10-8 C are located 16 cm apart. At what point(s) On the line there are two locations where potential becomes zero. For P, frac5 × 10⁻⁸x = frac3 × 10⁻⁸16-x 5( 16 - x) = 3x 80 - 5x = 3x 8x =... 1
- Two charges 2 μC and -2 μC are placed at points A and B 6 cm apart. (a) Identify an equipotential surface of the system (a) For the given system of the two charges, the equipotential surface will be a plane normal to the line AB joining the two charges and pas... 1
- The spherical conductor of radius 12 cm has a charge of 1.6 x 10-7 C distributed uniformly on its surface. R = 12 x 10⁻² m, Q = 1.6 x 10⁻⁷C (a) Zero (b) E = frac9 × 10⁹ × 1.6 × 10⁻⁷(12 × 10⁻²)² = frac9 × 10⁹ × 1.6 × 10⁻⁷12 × 12 × 10⁻⁴ = 10⁵ NC⁻¹ (... 1
- A parallel plate capacitor with air between the plates has a capacitance of 8 pF (lpF = 10-12F). C = 8pF, C = fracε₀ ~A~d C' = fracε_r ε₀ ~Ad/2 = 2ε_r ∴ C' = 2 x 6 x 8 x 10⁻¹² F = 96 pF 1
- In a parallel plate capacitor with air between the plates, each plate has an area of 6 x 10-3 m2 A = 6 x 10⁻³ m² d = 3 mm = 3 x 10⁻³m C = fracε₀ ~A~d = frac8.85 × 10⁻¹² × 6 × 10⁻³3 × 10⁻³ = 17.70 x 10⁻¹² = 17.7 pF Q = CV = 17.7 x 10⁻¹² x... 1
- A 12pF capacitor is connected to a 50V battery. How much electrostatic energy is stored in the capacitor? C = 12 pF, V = 50V E = 1 / 2 CV² = 1 / 2 x 10⁻¹² x 50 x 50 = 150 x 10⁻¹⁰ = 1.5 x 10⁻⁸ J 1
- Show that the force on each plate of a parallel plate capacitor has a magnitude equal to \(\frac { 1 }{ 2 }\) QE, where Force = 1 / 2 QE Work done = 1 / 2 V x Q The physical origin of the factor 1 / 2 in the force formula lies in the fact that just outside the... 2
- A μ piF capacitor is charged by a 200 V supply. It is then disconnected from the supply C₁ = 4 x 10⁻⁶F V = 200 V C₂ = 2 x 1o⁻⁶F E₁ = 1 / 2 C₁V² = 1 / 2 x 4 x 10⁻⁶ x 200 x 200 = 8 x 1o⁻² Q = C₁V = 4 x 10⁻⁶ x 200 = 8 x 10⁻⁴ C E₂ =... 1
- (a) Are potential difference and potential energy the same? (b) If they are not the same, then define them. (a) No. The potential difference is a field property. Potential energy is the interaction energy of charge configuration. (b) The electrosta... 1
- A proton and an electron move between two points having a potential difference V. (a) Both gain the same energy Work done = energy gain = Potential difference x Charge The p.d and charge are the same for each. (b) One eV i... 1
- ‘Work is done on the charge ’. What do you understand by this? While moving the charge, work is to be done against repulsion of the field. 1
- What is the potential difference between the surface and interior point of the charged conductor? The potential at every point in a charged conductor is the same and is equal to the potential on the surface. Therefore the potential differ... 1
- How can we increase the capacitance of a conductor? By increasing the linear dimension. 2
- How will the applied voltage be divided among the capacitors? In a series combination, the applied voltage divides among the capacitors in inverse proportion to their capacitances: V ∝ 1/C . In series,... 1
- In which form and where is the energy of the capacitor stored? Electrical energy and is stored between the plates in the form of the electric field. 1
- Classify the following molecules into (a) Polar and non-polar. (H2O, H2, NH3, N2, CO2, CO, HCl, O2) (a) Polar molecules: H2O, NH3, CO, HCl Non-polar molecules: H2, N2, CO2, and O2 (b) polar and non-polar molecules: A molecule is said to be... 1
- Two copper spheres of radii, one hollow and the other solid are charged to the same potential. Both will hold the same charge No The capacity is small 2
- How much work is done in moving a 500 pC charge between two points on an equipotential surface? zero the work done in moving the given charge between two equipotential surfaces is equal to zero. 1