Advertisements
Advertisements
Question
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?
Advertisements
Solution
In the expression U = Vit, voltage V and current i are variables for a given time interval. So, based on this expression we cannot say that U is proportional to i. In the expression U = i2Rt, the resistance R is fixed for a circuit for a given time interval. So, based on this expression, we can say that U is proportional to i2 and not i.
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.
Draw labelled graphs to show how electrical resistance varies with temperature for:
1) a metallic wire.
2) a piece of carbon
Consider a circuit containing an ideal battery connected to a resistor. Do "work done by the battery" and "the thermal energy developed" represent two names of the same physical quantity?
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?
Sometimes it is said that "heat is developed" in a resistance when there is an electric current in it. Recall that heat is defined as the energy being transferred due to temperature difference. Is the statement in quotes technically correct?
As the temperature of a metallic resistor is increased, the product of its resistivity and conductivity ____________ .
Two resistors R and 2R are connected in series in an electric circuit. The thermal energy developed in R and 2R are in the ratio ______________ .
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 2.0 Ω resistor shown in the figure is dipped into a calorimeter containing water. The heat capacity of the calorimeter together with water is 2000 J K−1. (a) If the circuit is active for 15 minutes, what would be the rise in the temperature of the water? (b) Suppose the 6.0 Ω resistor gets burnt. What would be the rise in the temperature of the water in the next 15 minutes?
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.
By increasing the temperature, the specific resistance of a conductor and a semiconductor -
The specific resistance of all the metals is the most affected by ______
Temperature dependence of resistivity ρ(T) of semiconductors, insulators and metals is significantly based on the following factors:
- number of charge carriers can change with temperature T.
- time interval between two successive collisions can depend on T.
- length of material can be a function of T.
- mass of carriers is a function of T.
Which expression gives resistance at a changed temperature?
Which microscopic relation for resistivity is given in terms of conductivity, electron mass, free-electron number density, electronic charge, and average relaxation time?
