Basic Circuit Elements

Basic Circuit Elements

Voltage Sources

Battery
  • Stores energy chemically.
  • Good for storing significant energy in a small space.
  • Provides a constant stream of energy for a long time.
  • Cannot release energy very quickly (low burst energy).
  • Connecting a battery directly to a low-resistance object (e.g., a paper clip) can cause it to overheat, degrade, or even explode.
  • Always include a resistor in a circuit with a battery to control current flow.
Capacitor
  • Stores energy electrostatically.
  • Great for high burst energy because charges can flow off the plates very quickly.
  • Difficult to store large amounts of energy compared to a battery.
  • Voltage changes as it releases energy; does not provide a constant voltage.
Generator
  • Does not store energy.
  • Transforms rotational energy into electrical voltage.
  • Can supply a large amount of total energy over a long time, as long as the rotational energy source is maintained.
  • Limited in burst energy; energy output is limited by the rate of rotational energy input.
  • Typically provides AC (alternating current) voltage.

Resistor

  • Slows down current within an electrical circuit.
  • Converts electrical energy into heat.
  • Many heating devices (toasters, hair dryers) consist of a battery or generator connected to a resistor.

Switch

  • A section of wire that can be moved to complete or break a circuit.
  • Open switch: circuit is incomplete, and current cannot flow.
  • Closed switch: circuit is complete, and current can flow.

Light Bulb

  • Symbol: a resistor symbol inside a circle (representing the glass bulb).
  • Incandescent light bulbs are super-hot resistors inside a glass bulb filled with a noble gas to prevent corrosion.
  • Converts electrical energy into light, with heat as a byproduct (due to the second law of thermodynamics).

Meters

Ohmmeter
  • Measures resistance.
  • Works by supplying a current through the resistor and measuring the voltage drop.
  • Must be used without any other power source in the circuit.
  • Connecting an ohmmeter to a circuit with a battery can damage the ohmmeter.
Voltmeter
  • Measures voltage (potential difference) between two points in a circuit.
  • Requires an energy source (battery, capacitor, or generator) to measure a non-zero voltage.
  • Connected in parallel to the component being measured.
  • V=IRV = IR (Ohm's Law)
  • For a bare wire with almost no resistance, the voltage drop is almost zero.
Ammeter
  • Measures current flowing through a segment of wire.
  • Must be placed inside the circuit, creating a break in the circuit for the current to flow through the ammeter.
  • Has very low resistance to avoid disturbing the current being measured.
  • Connecting an ammeter directly to a battery can cause a very large current to flow, potentially burning out the ammeter.
  • Ammeter should be in series with a resistor to control current flow.