Heating Effect Of Current
Cause of Heating Effect of Current
Consider a purely resistive circuit i.e. a ciruit which consist of only some resistors and a source of emf. The energy of the source gets dissipated entirely in the form of heat produced in the resistors. The phenomenon of the production of heat in a resistor by the flow of an electric current throught it is called heating effect of electric current or Joule heating.
When a potential difference is applied across the ends of a conductor, its free electron gets accelerated in the opposite direction of the applied field. But the speed of the electron does not increase beyond a constant drift speed. This is beacause during the course of their motion, the electron collide frequently with the positive metal ions. The kinetic energy gained by the electron during the intervals of free acceleration between collision is transferred to the metal ions at time of collision. The metal ions begin to vibrate about their mean position more and more violently. The average kinetic energy of the ions increases. This increases the temperature of the conductor. Thus the conductor gets heated due to the flow of current. Obviously, the electrical energy supplied by the source of emf converted into heat
Heat Produced by Electric Current :Joule's Law
Heat produced in a resistor. Consider a conductor AB of resistance R as shown in fig. A source of emf maintains a potential difference V between its ends. A and B and sends a steady current I from A to B. Clearly, Va> Vb and the potential difference across AB is V = Va-Vb> 0
The amount of charge that flows from A to B in time t is
q = It
As the charge q moves through a decrease of potential of magnitude V, its potential decreases by tha amount ,
U = Final P.E. at B - Initial P.E at A
qVb - qVa = -q(Va -Vb) = qV<0
If the charges move through the conductor without suffering collisions, their kinetic energy would change so that the total energy is unchanged. By conservation of energy, the change in kinetic energy must be
K = -U = qV = It × V = VIt> 0
Thus, in case, charges were moving freely throughb the conductor under the action of the electric field, the kinetic energy would increase as they move. However, we know that on the average, the charge carriers or electrons do not move with any acceleration but with a steady drift velocity. This is because of the collision of electrons with ions and atoms during the course of their motion. The kinetic energy gained by the electron is shared with the metal ions. These ions vibrate more vigorously and the conductor gets heated up. The amount of energy dissipated as heat in conductor in time t is
H = VIt joule = I^2Rt joule = V^2t/R joule
Or
H = VIt/4.18 cal = I^2Rt/4.18 cal = V^2t/4.18 R cal
According to this law, heat produced in the resistor is:
1. Directly proportional tobthe square of current for a given R
2. Directlt proportional to the resistance R for a given I
3. Inversaly proportional to the resistance R for a given V
4. Directly proportional to the time for which the current flows through the resistor.
Reference links :
Cause of Heating Effect of Current
Consider a purely resistive circuit i.e. a ciruit which consist of only some resistors and a source of emf. The energy of the source gets dissipated entirely in the form of heat produced in the resistors. The phenomenon of the production of heat in a resistor by the flow of an electric current throught it is called heating effect of electric current or Joule heating.
When a potential difference is applied across the ends of a conductor, its free electron gets accelerated in the opposite direction of the applied field. But the speed of the electron does not increase beyond a constant drift speed. This is beacause during the course of their motion, the electron collide frequently with the positive metal ions. The kinetic energy gained by the electron during the intervals of free acceleration between collision is transferred to the metal ions at time of collision. The metal ions begin to vibrate about their mean position more and more violently. The average kinetic energy of the ions increases. This increases the temperature of the conductor. Thus the conductor gets heated due to the flow of current. Obviously, the electrical energy supplied by the source of emf converted into heat
Heat Produced by Electric Current :Joule's Law
Heat produced in a resistor. Consider a conductor AB of resistance R as shown in fig. A source of emf maintains a potential difference V between its ends. A and B and sends a steady current I from A to B. Clearly, Va> Vb and the potential difference across AB is V = Va-Vb> 0
 |
| Cause of Heating Effect of Current |
q = It
As the charge q moves through a decrease of potential of magnitude V, its potential decreases by tha amount ,
U = Final P.E. at B - Initial P.E at A
qVb - qVa = -q(Va -Vb) = qV<0
If the charges move through the conductor without suffering collisions, their kinetic energy would change so that the total energy is unchanged. By conservation of energy, the change in kinetic energy must be
K = -U = qV = It × V = VIt> 0
Thus, in case, charges were moving freely throughb the conductor under the action of the electric field, the kinetic energy would increase as they move. However, we know that on the average, the charge carriers or electrons do not move with any acceleration but with a steady drift velocity. This is because of the collision of electrons with ions and atoms during the course of their motion. The kinetic energy gained by the electron is shared with the metal ions. These ions vibrate more vigorously and the conductor gets heated up. The amount of energy dissipated as heat in conductor in time t is
H = VIt joule = I^2Rt joule = V^2t/R joule
Or
H = VIt/4.18 cal = I^2Rt/4.18 cal = V^2t/4.18 R cal
According to this law, heat produced in the resistor is:
1. Directly proportional tobthe square of current for a given R
2. Directlt proportional to the resistance R for a given I
3. Inversaly proportional to the resistance R for a given V
4. Directly proportional to the time for which the current flows through the resistor.
Reference links :
Potentiometer: Construction | Principal | Application | Sensitivity
Heating Effect of Current
Reviewed by Being Morning Star
on
22:53
Rating:
Reviewed by Being Morning Star
on
22:53
Rating:
No comments: