Current Electricity

• Current


  Measure of the rate of electron flow past a given point in a circuit (e.g. how many electrons move past a certain point per second)
• Ammeter


  Device used to measure current, must be connected in series with a load
• Always set ammeter to highest setting when measuring a current
• Never touch the ends of the ammeter when connecting to a circuit
• Very large currents can damage electrical devices and cause an electrical fire
• Fuses and circuit breakers


  Devices connected in series with circuits that open if the current gets too high, stopping the current from flowing
• Even a small electrical shock can be dangerous
• 0.001 A - tingling sensation, 0.050-0.150 A - muscles contract and convulse, 1.0-4.3 A - heart stops
• PIPER: 'CURRENT EVENTS!'
• Series circuit


  Electrons follow one continuous loop, current is the same in all parts
• Parallel circuit


  Electrons have multiple paths, current splits into smaller currents
• Voltage (Potential Difference)


  Difference in electric potential energy per unit of charge measured at two points, the pressure that pushes electricity
• Voltmeter


  Device used to measure voltage, must be connected in parallel with a load or energy source
• Series circuit voltage


  Voltage adds up to total, each load gets a portion of the voltage
• Parallel circuit voltage


  Voltage is the same for each branch
• Electrical resistance


  Opposition to the movement of electrons as they flow through a circuit
• Ohmmeter


  Device used to measure resistance, must be connected in parallel with a load
• Factors affecting resistance


  • Type of material
  • Cross sectional area
  • Length of wire
  • Temperature
• Resistor


  Electrical device that reduces the current in a circuit
• Variable resistor


  Allows you to change the resistance in a circuit, used in dimmer switches and volume controls
• The current is the rate at which charge flows through an object.
• Current = Charge / Time
• Electric potential difference (V) is measured in volts (V). It's also called voltage or EMF.
• Current is measured in amperes (A) or amps.
• In a series circuit, all components are connected end-to-end so there is only one pathway for electricity to travel around the circuit.
• In a parallel circuit, two or more components are connected side by side so there are multiple pathways for electricity to travel around the circuit.
• Potential difference is the energy transferred from one charged object to another when they are brought together or separated.
• Potential difference is the energy per unit charge transferred between two points.
• Power (P) is measured in watts (W). Power is the rate at which energy is transferred.
• Voltage = Potential Difference