Understanding Electric Circuits and Current

Current

Flow of electrons.

Source

Provides energy (e.g., battery).

Load

Converts energy (e.g., bulb).

Switch

Controls flow (on/off).

Connectors

Path for electrons (e.g., copper wires).

Open Circuit

No flow.

Closed Circuit

Current flows.

Electric Current

Flow of charge in a circuit.

what is Charge measured in

Measured in Coulombs (C).

Formula for Current

I=Q/t.

1 Coulomb

6.2×10^18 electrons.

Electric Potential Energy

Energy stored in charge.

Voltage

Difference in energy before/after a load.

Formula for Voltage

V=E/Q.

Electrical Power

Energy used/produced per unit time.

Formula for Power

P=E/t and P=I×V.

Series Circuits

Current flows through one path.

Total Resistance in Series

RT=R1+R2+R3.

Parallel Circuits

Current splits into multiple paths; voltage is the same across branches.

Total Resistance in Parallel

1/RT=1/R1+1/R2+1/R3.

Electrical Efficiency

Percentage of energy input converted to useful energy.

Efficiency Formula

Efficiency=(Useful Energy Output/Total Energy Input)×100.

Unit of Energy

Kilowatt-hour (kWh).

Electricity Rates Off-peak

7.7 c/kWh.

Electricity Rates Mid-peak

11.4 c/kWh.

Electricity Rates On-peak

14.0 c/kWh.

Heater Energy Use

Power: 1.1 kW, Time: 3 hrs/day × 30 days, Total Energy = 99 kWh.

Light Bulb Comparison

100W bulb = 73 kWh/month, 7W LED bulb = 5.11 kWh/month.

PS3 vs Laptop Energy Use

PS3: 17.5 kWh/month, Laptop: 13.5 kWh/month.

Toaster Energy Use

Current: 8 A, Voltage: 110 V, Time: 3 hrs/month.

Resistance

The prevention of flow of electrons.

Friction

The friction created while an electron travels through a conductor.

Heat Release

Friction causes electrons to release energy inside the wire resulting in the release of heat.

Tungsten

Some metals, when heated up enough, glow/light up when heated.

Undesired Effects of Resistance

The waste created, such as heat, which means energy is wasted sometimes potentially making the circuit less effective.

Factors Influencing Resistance

Resistance is influenced by the length of the conductor, diameter of the conductor, and type of material.

Resistance Formula

R = V/I.

Resistance Unit

Ohms (Ω).

Charge Formula

I = Q/t.

Voltage Formula

V = E/Q.

Ohm's Law

R = V/I (voltage/current).

Series Circuit Resistance

Series circuit resistance is greater than parallel resistance circuit when using the same resistor.

Voltage Definition

The voltage (V) between two points is the energy per unit charge: V = E/Q.

Energy Calculation

The energy (E) can be calculated using: E = V × Q.

Charge Calculation

The charge (Q) can be calculated using: Q = E/V.

Power Definition

Power (P) is the rate at which energy is used or produced: P = E/t.

Power Calculation

Power can also be calculated as: P = V × I.

Current Calculation

The current (I) can be calculated using: I = Q/t.

Time Calculation

Time (t) can be calculated using: t = Q/I.

Energy in Joules

The energy in joules can also be expressed in terms of the charge and voltage: E = V × Q.