Download Circuits and Circuit Elements Schematic Diagrams and Circuits

Circuits and Circuit
Elements
Schematic Diagrams and Circuits
Schematic Diagrams and Circuits
• Schematic diagram – a representation of a circuit that
uses lines to represent wire and different symbols to
represent components
– Also called circuit diagrams
Electric
Circuits
Electric Circuits
Electric Circuits
• Electric circuit – a set of electrical components connected sbuch that
they provide one or more complete paths for the movement of
charges
• Charges move from the battery through a path back to the battery
• Load – any element or group of elements that dissipate energy
– Needs a source of potential difference and electrical energy (battery) and a
load (bulb)
• Circuits can be either open or closed
– Closed circuit – has a pathway through the circuit from one positive
terminal of the battery to the negative
– Open circuit – does not have such a pathway
Electric Circuits
• Overloaded – condition when electrical wires carry more
than a safe level of current
• Short circuit – accidental creation of an alternative
pathway
– Reduces the resistance in the circuit
– Increases the current
Electric Circuits
• Short circuits
– Leads to overload
– Occurs when a circuit does not have a load (no resistance)
• Wires cannot hold that much current, and their insulation may melt or
catch on fire
– Grounding is used to prevent electric shock from short circuits
Electric Circuits
• Circuit breaker – a device that protects a circuit from
current overloads
• Trip when the current overloads
– Acts like a switch
Electric Circuits
• The source of potential difference and electrical energy is
the circuit’s emf or electromotive force
– Emf - Energy per unit charge supplied by a source of electric
current
• Batteries and generators
• Terminal voltage is less than the emf
– Battery acts as both an emf and a resistor, although we will
ignore internal resistance of the battery
Electric Circuits
• Emf is not a true force
– Potential difference
– Voltage rating on a battery (1.5 V)
• Terminal Voltage = emf – current * resistance
• ΔV = ε - IR
Electric Circuits
• Potential difference across a load equals terminal voltage
• As charges move from one terminal to the other, the chemical
energy of the battery is converted into the electrical potential
energy of the charges
• As charges move through a circuit, their electrical potential
energy is converted to other forms of energy (kinetic, thermal,
light)
• Energy in a circuit must be conserved, so the energy gained in
the battery must be equal to the energy lost in the load
– Therefore, the potential increase across the battery must equal the
potential decrease of the load