Physical Sciences Break 1.0

Parts of a Simple Circuit

1. EMF and Potential Difference:

• Electromotive Force (EMF): The energy provided by a battery or cell per coulomb of charge passing through it. It’s the maximum potential difference when no current is flowing.
• Potential Difference (Voltage): The work done to move a unit charge from one point to another.

1. Battery or Cell: Provides the necessary EMF to drive the current around the circuit.
2. Electric Current:

• The flow of electric charge (usually electrons) around a circuit.
• Measured in amperes (A).

1. Measuring Current:

• Ammeter: An instrument used to measure electric current.
• Connecting an Ammeter: Must be connected in series with the component whose current you want to measure.

1. Conventional Current vs. Electron Current Flow:

• Conventional Current: Defined as flowing from the positive terminal to the negative terminal of the battery.
• Electron Current Flow: Electrons flow from the negative terminal to the positive terminal.

1. The Voltmeter:

• Potential Difference: The voltmeter measures the potential difference between two points in a circuit.
• Connecting a Voltmeter: Must be connected in parallel with the component whose voltage you want to measure.

Possible Wiring Plan

• To measure current through a resistor, place the ammeter in series with the resistor.
• To measure the voltage across the resistor, place the voltmeter in parallel with the resistor.

Resistors in Series and Parallel

1. Series:

• Total resistance, ( R_{total} ): ( R_1 + R_2 + R_3 …
• Current through each resistor is the same.
• Voltage across each resistor is different.

1. Parallel:

• Total resistance, ( \frac{1}{R_{total}} ): ( \frac{1}{R_1} + \frac{1}{R_2} + \frac{1}{R_3} + \ldots )
• Voltage across each resistor is the same.
• Current through each resistor is different.

Equation of Electric Circuits

1. Ohm’s Law: ( V = IR )

• ( V ): Voltage (Volts)
• ( I ): Current (Amperes)
• ( R ): Resistance (Ohms)

1. Kirchhoff’s Laws:

• Kirchhoff’s Current Law (KCL): The sum of currents entering a junction equals the sum of currents leaving the junction.
• Kirchhoff’s Voltage Law (KVL): The sum of all voltages around a closed loop equals zero.

Practical Example

For a circuit with a battery, a resistor, an ammeter, and a voltmeter:

1. Ammeter: Connect in series with the resistor to measure the current.
2. Voltmeter: Connect in parallel with the resistor to measure the voltage drop across it.

Diagram of Simple Circuit

  +----(A)----R-----
  |                |
  |                V
 (+)              (-)
Battery           |
  |                |
  ------------------

In this diagram:

• A represents the ammeter connected in series.
• R is the resistor.
• V represents the voltmeter connected in parallel.
• Battery provides the EMF.

This is a basic overview of the concepts and components in a simple electric circuit. If you need more detailed explanations or have specific questions, feel free to ask!