Fundamentals of Electric Circuits and Battery Basics

Battery Basics

Batteries drive electric current via chemical reactions that transfer electrons from one terminal to another.

Electromotive Force (EMF, ε)

The maximum potential difference a power source can provide.

EMF Measurement

Not an actual force; measured in volts (V) or joules per coulomb (J/C).

Voltage (Potential Difference)

Acts like electrical pressure, pushing and pulling charges through a conductor.

Voltage Driving Current

Voltage drives current by pushing electrons from the negative terminal (where there are extra electrons) to the positive terminal (where there is an electron deficit).

Voltage Measurement

Measured in volts (V).

Basic Parts of an Electric Circuit

1. Source of energy (e.g., battery) 2. Closed path (e.g., wires making a loop) 3. Device that uses energy (e.g., lightbulb).

Open Circuit

An open circuit = the device will not work.

Water Pump Analogy

Two important pump/circuit principles: A pressure difference (start to end) and the amount of flow per second.

Circuit Principles

Potential difference (voltage): drives charge from start to end.

Current (I)

Amount of charge that flows per second (measured in amperes, A).

Conventional Current

Describes the flow of positive charges from high to low potential.

Electric Resistance

How much a material resists charge flow.

Resistance Units

Units: Ohms (Ω, uppercase Greek Omega).

Resistance Effect

Resistance turns electrical energy into heat/light (example: filament in a bulb).

Factors Affecting Current

Amount of current depends on: Voltage from the source and electrical resistance of the conductor.

Resistor

Restricts current flow.

Real Device Resistance

Every real device has some resistance.

Resistance and Current

More resistance = less current.

Voltage Loss

Resistance causes some voltage to be lost across it.

Energy & Power Consumption

Kilowatt-Hour (kWh): Energy used in 1 hour at a rate of 1 kW (1000 watts).

Cost of Electricity Example

If electricity is 5¢ per kWh, running a 100W light bulb for 10 hours costs 5¢.