Define internal resistance of a cell.
Prove that r = , where R is the external resistance used.
Two resistance filaments of same length are connected first in series and then in parallel. Find the ratio of power dissipated in both cases assuming that equal current flows in the main circuit.
Plot a graph showing the temperature dependence of resistivity for a typical semiconductor.
How is this behaviour explained?
A cell of emf E is connected across an external resistance R. When current I is drawn from the cell, the potential difference across the electrodes of the cell drops to V. The internal resistance r of the cell is
Define relaxation time of the free electrons drifting in a conductor.
How is relaxation time related to the drift velocity of free electrons?
Use this relation to deduce the expression for the electrical resistivity of the material.
A cell of emf (E) and internal resistance r is connected across a variable external resistance R. The graph of terminal potential difference V as a function of R is-
A battery of emf 12 V and internal resistance 2 is connected to a 4 resistor as shown in the figure.
Show that a voltmeter when placed across the cell and across the resistor, in turn, gives the same reading.
A heating element is marked 210 V, 630 W. What is the value of the current drawn by the element when connected to a 210 V DC source?
The internal resistance of a cell:
The dimension of electrical resistance is: