The Garden Hose

When the resistance increases, and the current is constant, the pressure increases:

The same thing is true of electrical circuits:

If R increases, V has to increase to keep their quotient (I) constant.

would happen to the pressure if you decrease the flow (by turning down the faucet) while keeping the nozzle on the hose (constant resistance)?

Current, Voltage, and Resistance

These three are related by a very simple equation:

Take a minute and reflect on the relationship between these three components. Think of it like it's a garden hose:

The current is water flowing in the hose. The water pressure is analogous to the voltage of a circuit and the diameter of the hose determines the resistance.

happens when you put a nozzle on end of the hose? In this case, the resistance increases with a constant amount of water flowing through it. What happens to the pressure?

The Basic Electrical Circuit

Electrical circuits involve 3 basic components:

is the force created by the separation of charges. Kind of like when two opposite poles of a magnet are put close together, but are separated by a short distance. A force tries to pull them together. When there are more negative charges on the inside of the membrane of a cell, there is a force driving positive charges inward to neutralize them. The unit of voltage is the volt and it is represented by the symbol V. Voltage is also called "potential" or "potential difference".

is a measure of how hard it is for charges to move in the system. In a cell, the lipid portion of the membrane is impermiable to ions, so the resistance to current across the membrane is determined by the opening and closing of ion channels. When the channels open, the resistance decreases. When they close, resistance increases (because ions can't move through the membrane). The units of resistance are ohms and it is represented by the symbol R. (Note - When talking about channels, "conductance" is usually used instead of resistance. Conductance is the inverse of resistance (1/R), or how easy it is to pass charges. Its units are seimans [S].)

is the movment of charges. In an electrical circuit, electrons move from the negative pole to the positive pole (although electrical current is defined as the movement of positive charges, so current is said to go from the positive pole to negative pole - go figure). In cells, current is when ions move through the membrane (usually Na⁺, K⁺, Ca²⁺, or Cl^-).

Test your knowledge - Electrical

1. The unit of measurement of electrical current produced in a circuit by 1 volt acting through a resistance of 1 ohm? Amp Volt Watt Ohm

2. If the Voltmeter reading is 12V, and the Ammeter reading is 3A, what is the resistance? 4 Amps 4 Ohms 36 Ohms 4 Volts

3. The unit of measurement of electrical resistance. The resistance of a circuit in which a potential difference of 1 volt produces a current of 1 ampere. Volt Watt Amp Ohm

4. An electromagnetic device for changing the voltage of alternating current (AC) electricity. Winding Stator Transformer Rotor

5. A device consisting of two conducting surfaces separated by an insulator and having the ability of storing electric energy. Diode Capacitor Resistor Vacuum Tube

6. An element of an electron tube or semiconductor device that takes part in conduction, such as the plate, anode, cathode and filament. Electrode Diode Capacitor Resistor

7. The ratio of watts to volt-amperes of an AC electric circuit. Horse Power Resistance Power Factor Inductance

8. The stationary part of a rotating electric machine. Commonly used to describe the stationary part of an AC machine that contains the primary windings. Rotor Stator Core Winding

9. The preferred terminology for cycles per second (frequency). Hertz (HZ) RPM Ohm Farad

10. A unit of capacity that will store one coulomb of electrical charge when one volt of electrical pressure is applied. Hertz (HZ) Capacitance Inductance Farad

11. A piece of rigid metal within a panel or fusebox which distributes electricity to the various circuits by means of their connection to it. Busbar Terminal Contact Splitter

12. A device that interrupts current to its circuit by melting apart. It must then be replaced. Circuit breaker Fuse Diode Wire

13. The flow of electrons in a wire. Amp Volt Current Inductance

14. A measure of the work electricity can do. Watt Horse Power Amp Foot-pounds

15. A material is considered to be a conductor of electricity if it has? Multiple neutrons No electrons No neutrons Free electrons

16. The most commonly used conductor of electricity is? Aluminum Copper Mercury Gold

17. Resistance is measured in? Ohms Watts Volts Amps

18. The symbol for Amperage is? I E R W

19. Materials which allow electricity to pass through them are? Wires Busbars Terminals Conductors

20. Which of these would be the best conductor of electricity? Saltwater Air Glass Rubber Glove