AIM: To determine the dielectric constant of the dielectric medium present in a parallel plate capacitor.
APPARATUS: DC Regulated power supply, Electrolytic capacitor, Resistor, Digital voltmeter, Digital timer, Double plug key.
PRINCIPLE: Capacitors are devices which store electric energy by means of an electrostatic field and release this energy later. The voltage across the capacitor when it gets charged gradually at any instant of time t, is given by
Vc = V (1-e-t/RC),
where V is the voltage applied, R is the resistance and C the capacitance in the circuit. While discharging through the resistor R, the capacitor voltage at any instant t is given by,
Vc = V e-t/RC
Let T1/2 be the time required to charge or discharge a capacitor to 50%.
\When t= T1/2, Vc = V/2
V/2 = V e-t/RC
et/RC = 2
t/RC = loge 2 = 0.693
C = T1/2 /0.693 R
But C = Ke0A/d where A and d are the thickness and area of the dielectric material. e0 is the permittivity of free space and K the dielectric constant.
\K = d T1/2 /0.693e0AR
PROCEDURE: The circuit connections are made as shown in figure.
To begin with, the toggle key H is connected to point 1. Now the capacitor begins to get charged to higher voltage. The voltage across the capacitor is taken at every 10 seconds interval from the 0th second until capacitor voltage becomes practically constant. Now the capacitor is fully charged.
Now the toggle key H is connected to point 2. The voltage across the capacitor is taken at every 10 seconds interval from the 0th second until capacitor voltage becomes practically zero.
A graph is plotted with time T taken along X-axis and the capacitor voltage V along Y-axis. The charging mode curve and the discharging mode curve intersect at the point P. By referring the position ‘P’ to the time axis, the value of its abscissa T1/2 in seconds is found out. Now the dielectric constant K can be calculated.
APPARATUS: DC Regulated power supply, Electrolytic capacitor, Resistor, Digital voltmeter, Digital timer, Double plug key.
PRINCIPLE: Capacitors are devices which store electric energy by means of an electrostatic field and release this energy later. The voltage across the capacitor when it gets charged gradually at any instant of time t, is given by
Vc = V (1-e-t/RC),
where V is the voltage applied, R is the resistance and C the capacitance in the circuit. While discharging through the resistor R, the capacitor voltage at any instant t is given by,
Vc = V e-t/RC
Let T1/2 be the time required to charge or discharge a capacitor to 50%.
\When t= T1/2, Vc = V/2
V/2 = V e-t/RC
et/RC = 2
t/RC = loge 2 = 0.693
C = T1/2 /0.693 R
But C = Ke0A/d where A and d are the thickness and area of the dielectric material. e0 is the permittivity of free space and K the dielectric constant.
\K = d T1/2 /0.693e0AR
PROCEDURE: The circuit connections are made as shown in figure.
To begin with, the toggle key H is connected to point 1. Now the capacitor begins to get charged to higher voltage. The voltage across the capacitor is taken at every 10 seconds interval from the 0th second until capacitor voltage becomes practically constant. Now the capacitor is fully charged.
Now the toggle key H is connected to point 2. The voltage across the capacitor is taken at every 10 seconds interval from the 0th second until capacitor voltage becomes practically zero.
A graph is plotted with time T taken along X-axis and the capacitor voltage V along Y-axis. The charging mode curve and the discharging mode curve intersect at the point P. By referring the position ‘P’ to the time axis, the value of its abscissa T1/2 in seconds is found out. Now the dielectric constant K can be calculated.
OBSERVATIONS:
R=
R=
Length L=
Breadth b=
Thichness d=
Area A= L × b=
Time (s) Voltage during charging (V) Voltage during discharging (V)
Breadth b=
Thichness d=
Area A= L × b=
Time (s) Voltage during charging (V) Voltage during discharging (V)
CALCULATIONS:
K = d T1/2 /0.693e0AR=
RESULT: The dielectric constant of the material in the given capacitor =
7 comments:
What is the use of the resistor shown in the circuit?
What is the use of the resistor shown in the circuit?
It is used to discharge the capacitor
It is used to discharge the capacitor
What happen if dielectric material is removed?
Can u add picture of setup with connections
To give the required voltage to voltmeter and capacitor
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