What is the difference between operating a transistor as a switch and as an amplifier?
When a transistor is used as a switch it is fully turned ON and OFF by a control signal usually applied between the base and the emitter. This causes the collector to emitter resistance to drop to a low value.. much like a simple electrical switch. Common electrical components such as lamps can be connected in series with the power supply voltage and the collector and emitter of the transistor.
This allows a small control current applied to the base of the transistor to control a much larger current through the lamp.
See here for more: Transistors as switches
When used as an amplifier the transistor operates in a linear region between cutoff and saturation (Not fully on or off).
When the base current is set to operate the transistor in this region, it can be used to amplify a input voltage or current in a linear fashion.
This usually requires additional resistors to set this operating point.
Different configurations that be used to make a current amplifier (no voltage amplification), or voltage amplifier depending on the application.
See here for more: Basic Transistor Amplifiers
A semi-conductor can made from silicon, germanium (and a few other elements) by adding small amounts of other elements in a process called “Doping” (no relation to illegal drugs).
Two different types of semiconductors can be made in this process (called P and N type).
A semi-conductor can be made to act like either a conductor or an insulator depending on the applied voltage polarity.
P and N type semiconductors are combined to make diodes, transistors, scrs and other electronic components.
See more here:
Doping to make semiconductors
How do you measure voltage in a circuit?
Yes, you need to use a voltmeter or a multimeter with a voltage scale.
Voltage is always measured with respect to 2 points in an electrical circuit.
Most DC circuits use a common output of the power supply(usually the negative) for one of the points and call this ground (abbreviated GND). The black terminal of your meter should be attached to this point, while the red lead is used to measure voltages in the rest of the circuit with respect to this ground point.
AC circuits also use a common ground point but the polarity of the leads is not as critcal since AC voltage doesn’t have a “polarity”.
If you have an Ultracapacitor with the below specs…
Boostcap® Ultracapacitor
3000.0 Farad ± 20%; 2.7V
How many would you need to store 1KWH of energy? ( 1,000 watts for an hour)
The energy in Joules stored in a capacitor can be calculated with the following formula
E=(1/2) C V^2
for C=3000F V=2.7 Volts
E=10935 Joules
1Kwh = 3,600,000 Joules
Therefore you would need
3600000/10935 = 329.2 or rounding up
330 capacitors to supply 1Kwh of energy
Modern ultracapacitors are now approaching the energy density of the best batteries and have the advantage of very rapid charge and discharge currents
The device shown at the following link is very similar to the calculated result shown above
Capacitor Bank
These links are very useful for these sorts of calculations:
Energy storage in a capacitor
Energy equivalents
Two inductors having inductances L1= 5H and L2=2H and are connected in parallel. The mutual inductance M between the two inductors is 1H. Determine the equivalent inductance (in H) for this system.
With mutual inductance the combined inductance is more complicated to calculate
M=1H
1/Ltotal =( L1 + L2 – 2(M)) / (L1L2 – M^2)
1/Ltotal = (7-2) / (10-1)
1/Ltotal = 5/9
Ltotal = 1.8 H
See also this page for future reference
Series and parallel circuits
The primary purpose of diodes is to allow electrical current to flow in only one direction.
The primary purpose for power diodes is as components of power supplies that are used to convert AC (Alternating Current) line voltage (from the wall socket) into DC (Direct Current) to power an electronic device.
Diodes are typically rated based on 2 numbers:
(1)Maximum current they can carry
(2)The maximum reverse voltage they can withstand (also called PIV or Peak Inverse Voltage)