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Basic Electronics
• What is electricity?• How is it measured?• Terms• Ohm’s Law • Kirchhoff's Laws• Power• Putting it together• Power Distribution
What is electricity
• Electricity is the flow of electrons in a conductor
• Electricity is measured in:– Voltage (V) – similar to pressure, this is the force
available to drive the electricity measured in Volts– Current (I) – this is the flow of the electricity
measured in Amps– Power (W) – this is the power used or available
measured in Watts
Other electrical terms• Resistance
– a measure of a material’s resistance to the flow of electricity– measured in ohms Ω
• AC Current – current that flows first in one direction then in the opposite direction
• DC Current – current that flows in one direction
• Open Circuit – a broken current path
• Close Circuit – a complete current path
• Short Circuit – when current does not flow where intended
Ohm’s Law
V=IRVoltage equals Current times Resistance
• What can cause Resistance?– Wires; the smaller the wire or the longer the run
the greater the resistance– Circuitry– Bad Connections– Anything between the power source and the load
Kirchhoff's Laws
• Voltage – There must always be a closed path for current to
flow– Summation of voltages around any closed loop is 0
• Current – Summation of currents into a node must equal 0
Putting it together
Simple Circuit
If V is 10 Volts and R is 10 ohms, what is I?What is the power used by the Resistor?
Resistor (R)Battery (V)
+
-
V1 V2Current (I)
Motor Circuit
If V is 10 Volts and RM is 10 ohms, what is I?What is the power used by the Motor?
If V is 10 Volts and R and RM are 10 ohms what is I?What is the power used by the Motor?
Putting it together cont.
Motor(RM)
V
+
-
V1 V2
R
V3
I
Putting it together cont.
The resistance of a motor is not simple and does not follow the previous example the amount of current used by a motor is dependent on the load. Let’s redo the previous calculation assuming the motor has a 10 Watt load.
Putting it together cont.Motor Circuit
If V is 7 Volts and R is 1 ohms and the Motor uses 10 Watts, what is I?7 = V2 + V3
W = VI => V = W/I7 = I + 10/I
I=2, 5There are two answers, how can this be? As the voltage drops the motor will slow down, producing less power, reducing the need for current - even
here the motor is not linear
Motor(RM)
V
+
-
V1 V2
R
V3
I
Application
• How do we reduce the resistance to the motor?– Larger Wires– Shorter Wire runs– Better/Fewer connections
Power Distribution
• What is Power Distribution?– Providing power from the battery to the devices
that need it.• Why is it important?– Safety– Clean distribution • efficient and allows for better performance• Easier modification and troubleshooting
Power Distribution
• What does it look like?• One device or load• What about more?
LoadBattery (V)
+
-
Load Load
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