Doubtly
@Doubtly · Joined Feb 2021
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- How can you compare the emf of two cells? Using potentiometer we can compare the emf of two cells. 2
- What is meant by the internal resistance of a cell? Internal resistance of a cell is defined as the resistance offered by the components inside it to the flow of current. The value of internal... 1
- If a person touches a live wire, will he get stuck to it? Why do we use copper wires as connecting wires? Sometimes. Even very small currents are enough to disorganise our nervous system. Hence the affected person may temporarily lose his ability... 1
- Light from a bathroom bulb gets dimmer for a moment when Geiser is switched on. Why? Since the resistance of the geiser is less than that of a bulb, geiser draws more current from the mains than the bulb. So the bulb becomes... 1
- In the above figure, the numbers 1, 2, 3 and 4 have got some meaning. (a) What is the meaning of each number? (a) The first coloured band (1) gives the first significant figure, second coloured band (2) gives second significant figure, third coloured... 1
- What is conventional current? The current which flows from the positive to negative end of a cell in the external circuit is called conventional current. 1
- What is the significance of the direction of the current? The direction of the conventional current is opposite to the flow of electrons. The direction of electronic current is in the direction of t... 1
- How does drift velocity of electrons in a metallic conductor vary with temperature? The drift velocity of electrons in a metallic conductor decreases with an increase in temperature. 1
- Why are connecting wires made of copper? Copper has very low resistivity (high conductivity). Also copper is a diamagnetic material, so it is not magnetised due to the flow of curre... 1
- 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