HANDS-ON EXPERIMENTS9.1 DC Voltage

HANDS-ON EXPERIMENTS
9.1 DC Voltage Sources
Lab objectives
The objective of this hands-on is to determine experimentally the internal impedance of a voltage
source and to plot its external characteristic graph.
Background Information
An ideal DC voltage source is such an electric energy source that the potential difference between its
output terminals is independent on the external circuit current. The potential difference in a real DC
source depends, to a certain degree, on the external circuit current. In real life this dependence is
usually linear or nearly linear:
DV = DI × r0 , (1)
where
DV the absolute value of potentials difference between voltage source terminals
DI the external circuit current change
0 r the voltage source internal impedance, 0
r V
I
=
DV = E -V , (2)
where
E the voltage source’ electromotive force (EMF) - the potential difference between voltage
source terminals when I=0
V the voltage applied to the external circuit
If DI = I , we can obtain from (1) and (2) the dependence of voltage at the output terminals on load
current: 0 V = E - I × r . This dependence is called the external characteristic of the voltage source (Fig.
9.1-1). This expression is valid if the external circuit current does not exceed the admissible range, as
determined by the voltage source physical characteristics.
HANDS-ON EXPERIMENTS
9.1 DC Voltage Sources
Lab objectives
The objective of this hands-on is to determine experimentally the internal impedance of a voltage
source and to plot its external characteristic graph.
Background Information
An ideal DC voltage source is such an electric energy source that the potential difference between its
output terminals is independent on the external circuit current. The potential difference in a real DC
source depends, to a certain degree, on the external circuit current. In real life this dependence is
usually linear or nearly linear:
DV = DI × r0 , (1)
where
DV the absolute value of potentials difference between voltage source terminals
DI the external circuit current change
0 r the voltage source internal impedance, 0
r V
I
=
DV = E -V , (2)
where
E the voltage source’ electromotive force (EMF) - the potential difference between voltage
source terminals when I=0
V the voltage applied to the external circuit
If DI = I , we can obtain from (1) and (2) the dependence of voltage at the output terminals on load
current: 0 V = E - I × r . This dependence is called the external characteristic of the voltage source (Fig.
9.1-1). This expression is valid if the external circuit current does not exceed the admissible range, as
determined by the voltage source physical characteristics.