Currents & Concepts
The Trinity of Electricity—How Push, Flow, and Opposition Shape Every Circuit
What Is Voltage?
Definition: Voltage is the electrical potential difference between two points. It’s what pushes electrons through a circuit.
Unit: Volts (V)
Analogy: Think of voltage like water pressure in a pipe. The higher the pressure, the more forcefully water (or in this case, electrons) will try to move.
Real-world Example: A 9V battery pushes harder than a 1.5V AA battery. Your handheld ham radio might use 7.2V from a lithium pack, while your home power supply might give 13.8V.
What Is Current?
Definition: Current is the flow of electric charge, or how many electrons move past a point in a given time.
Unit: Amperes (Amps, A)
Analogy: If voltage is pressure, current is the flow rate of water. High current means more water (electrons) are flowing per second.
Types:
Direct Current (DC) – flows in one direction (batteries).
Alternating Current (AC) – changes direction (wall outlet, power lines).
In Ham Radio: Your transceiver draws current when it transmits. A 100-watt HF rig may draw 20 amps from your power supply at full power.
What Is Resistance?
Definition: Resistance is the opposition to current flow within a material or circuit.
Unit: Ohms (Ω)
Analogy: Resistance is like narrow sections of pipe that slow water down. More resistance = less current for the same voltage.
Materials: Copper has low resistance; carbon and rubber have high resistance.
Resistors: Deliberate components used to control current and divide voltage in a circuit.
Ohm’s Law: The Golden Rule
The relationship between these three properties is defined by Ohm’s Law:
V = I × R
Where:
V is voltage (in volts)
I is current (in amps)
R is resistance (in ohms)
Rearranged:
I = V / R
R = V / I
Why These Matter in Ham Radio
The relationship between these three properties is defined by Ohm’s Law:
V = I × R
Where:
V is voltage (in volts)
I is current (in amps)
R is resistance (in ohms)
Rearranged:
I = V / R
R = V / I
Why These Matter in Ham Radio
|
Scenario |
Voltage |
Resistance | Current | |
|---|---|---|---|---|
| You connect a 9V battery to a 3Ω resistor | 9V | 3Ω | 3A | |
| You use a 12V power supply on a 4Ω load | 12V | 4Ω | 3A | |
| You want only 1A current from a 9V battery | 9V | ? |
1A → R = 9Ω |