Electricity: Basic Concepts Review
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Ohm’s Law
- Ohm’s Law describes the relationship between the Voltage (V), Current (I) and Resistance (R) of a circuit
- It is stated as V = I.R
- I = V/R and R = V/I naturally follows
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Pic Courtesy : https://www.instructables.com/id/Ohms-Law-for-Dummies/
Voltage, Current and Resistance
Voltage (V):
- A measure of potential energy in a circuit.
- Units: Volts (V)
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- Opposition to charge flow.
- Units: Ohms (Ω)
Current Flow Analogy
Voltage Analogy
Resistance Analogy
A simple circuit is given below, where the 3V battery causes a current through the LED, causing it to light up.
Measuring Electricity – Voltage
Voltage is a measure of potential electrical energy. A voltage is also called a potential difference – it is measured between two points in a circuit – across a device by connecting a voltmeter in parallel with the device. In practice, we use a multimeter - which can also measure current and resistance with an appropriate selection (usually a knob).
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Tinkercard has a multimeter. You can build circuits and make appropriate measurements!
Measuring Electricity -- Current
Current is the measure of the rate of charge flow. For Electrical Engineers – we consider this to be the movement of electrons.
In order to measure this – you must break the circuit or insert the meter in-line (series).
Measuring Electricity -- Resistance
Resistance is the measure of how much opposition to current flow is in a circuit
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Now, we also incorporate the measurement of voltage across the resistor. We can verify that Ohm's law holds: 1.08V/3.26 mA = ~330 Ohm.
Prototyping Circuits : Breadboard
One of the most useful tools in an engineer or Maker’s toolkit
- A breadboard is easier than soldering
- A lot of those little holes are connected, which ones?
Solderless Breadboard
Each row (horizontal) of 5 holes are connected
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Longer breadboards have the vertical connections broken in the middle – think of them as 2 separate small breadboards
You can use a virtual breadboard and wire up stuff in Tinkercad!
Using Breadboard
Use the breadboard to wire up a single LED with a 220 Ohm (Red-Red-Brown) or 330 Ohm Resistor (Orange-Orange-Brown)
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Note: the longer leg on the LED is the positive leg (green wire, connect to 5V) and the shorter leg is the negative (black wire, connect to 0V)
Blinking the LED
Move the green wire from the power pin to pin 13 on the Arduino board without changing the program. The LED should blink.
Now try changing the connection from pin 13 to pin 11 (as shown in the image). How should your program be modified for the LED to blink?
Good Wiring Practices
Following good wiring practices can help you save a lot of time and trouble during debugging / modifying your circuit. Following the following rules might sound unnecessary at first, but you will realize later that the time spent is more than worth it.
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