Basic Concepts of Electricity – KNOW THESE CONCEPTS
- Voltage, current, and resistance are linked in an electrical circuit. When resistance goes up, current goes down. When resistance drops, current goes up.
- Voltage is a measurement of a difference of potential.
- Current is the speed of the electrons
- Resistance is the backpressure or force opposing the movement of electrons.
- All electrical circuits have the following components:
- Source – where the electrical current comes from
- Path – the wire or path the electricity travels
- Switch – a device to control the electricity
- Load – a device that uses the electric current to do work.
- An open switch has infinite resistance and thus does not allow current to pass.
- A closed switch has little resistance and allows current to pass.
- In any switching device the greater the resistance, the greater the heat generated. We want as little resistance as possible.
- Voltage is a measurable difference in potential.
- Voltage across a closed switch is 0 volts.
- Voltage across an open switch is source.
- Voltage across a working load is source or a portion of source.
- Voltage across a non-working (or open) load is the same as an open switch, it is source.
- A short circuit is a path (may have a switch) that does not have a load. The current will move to fast, go way up, and cause the circuit breaker or fuse to open.
- A closed circuit is a complete path for electricity to flow.
- Ohms Law is the basis behind all electric theory. Ohms law is:
- E = I * R
- I = E/R
- R = E/I
- Where E is Voltage
- R is resistance
- I is current
- A Series circuit has a single path for current to flow.
- A Parallel circuit has multiple paths for current to flow.
- Ohms law works for both series and parallel circuits.
- However, resistance ADDS up to total in a series circuit
- Current is constant in a Series circuit.
- Current ADDS up to a total in a parallel circuit.
- Resistance uses 1/Rt = 1/R1 + 1/R2 + 1/R3…. in a parallel circuit.
- Voltage is split across all loads in a series circuit based on the resistance of that load.
- Voltage is source for all BRANCHES in a parallel circuit.
- When voltage is applied to a coil of wire, it creates a magnetic field.
- The picture of alternating current is the sign wave. A magnet spinning in a coil of wires creates alternating current. Alternating current is what is used in houses and businesses. With Alternating current the voltage (or potential) shifts from positive to negative.
- The measurement of this frequency of change is Hertz.
- In the United States, the frequency is 60Hz or 60 times per second.
- In Europe, this change occurs 50 times per second or 50 Hz.
- A picture of a circuit is called a schematic diagram.
- A schematic diagram is made up of schematic symbols.
- A schematic diagram can be used to trace or understand a circuit in the field.