Advertisements
Advertisements
Question
A variable resistor R is connected across a cell of emf ε and internal resistance r as shown in the figure. Draw a plot showing the variation of
(i) Terminal voltage V and
(ii) the current I, as a function of R.
Advertisements
Solution
(i) Terminal voltage across a cell as a function of R
As resistance R increases current (I) in the circuit decreases and terminal voltage (V) increases.
We know V = ε –Ir; Where ε is emf of the cell
(ii) Current I as a function of R.
The current across a cell is given by `"I" = epsilon/("R"+"r")`
When R increases I decreases
APPEARS IN
RELATED QUESTIONS
A silver wire has a resistance of 2.1 Ω at 27.5°C, and a resistance of 2.7 Ω at 100°C. Determine the temperature coefficient of resistivity of silver.
A heating element using nichrome connected to a 230 V supply draws an initial current of 3.2 A which settles after a few seconds to a steady value of 2.8 A. What is the steady temperature of the heating element if the room temperature is 27.0°C? The temperature coefficient of resistance of nichrome averaged over the temperature range involved is 1.70 × 10−4 °C−1.
The order of coloured rings in a carbon resistor is red, yellow, blue and silver. The resistance of the
carbon resistor is:
a) 24 x 106 Ω ± 5%
b) 24 x 106 Ω ± 10%
c) 34 x 104 Ω ± 10%
d) 26 x 104 Ω ± 5%
The thermal energy developed in a current-carrying resistor is given by U = i2 Rt and also by U = Vit. Should we say that U is proportional to i2 or i?
Is work done by a battery always equal to the thermal energy developed in electrical circuit? What happens if a capacitor is connected in the circuit?
As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity ____________ .
An electric kettle used to prepare tea, takes 2 minutes to boil 4 cups of water (1 cup contains 200 cc of water) if the room temperature is 25°C. (a) If the cost of power consumption is Re 1.00 per unit (1 unit = 1000 watt-hour), calculate the cost of boiling 4 cups of water. (b) What will be the corresponding cost if the room temperature drops to 5°C?
The figure shows an electrolyte of AgCl through which a current is passed. It is observed that 2.68 g of silver is deposited in 10 minutes on the cathode. Find the heat developed in the 20 Ω resistor during this period. Atomic weight of silver is 107.9 g/mol−1.
A carbon resistor has coloured bands as shown in Figure 2 below. The resistance of the resistor is:
figure 2
The higher and lower fixed points on a thermometer are separated by 160 mm. When the length of the mercury thread above the lower point is 40 mm, the temperature reading would be :
