Electricity Flashcards
What is current, and what is the symbol for current?
Current = the flow of electrons (negative charge)
Symbol - I or i
What is the unit of current?
Amps (A)
*always measured as the flow through something
What is voltage, and what is the symbol for voltage?
Volgate = electromotive force (electric potential) that makes electrons move
Symbol - E or e
What direction do electrons move?
In the direction of a positive voltage difference
What is the unit for voltage?
Volts (V)
*always measured from one to point another, with respect to a reference (e.g., “ground potential” = Earth as a reference point)
What is direct current?
Current that flows in one direction all the time (dc)
What is alternating current?
Current that regularly reverses direction (ac)
What is dc voltage?
Voltage that has the same polarity (same direction from positive to negative voltage) all the time
What is ac voltage?
Voltage that regularly verses polarity
What is a circuit? What is an electrical circuit made of?
Circuit = path through which current can flow
An electrical circuit is made of components
What type of electric circuit has the same current through all components?
Series circuit
What type of electric circuit has the same voltage present across all components?
Parallel circuit
*Initial current will be divided across number of parallel components
What does an ohmmeter measure?
Resistence in a circuit
What meters does a multimeter include?
Voltmeter, ammeter, ohmmeter
What is resistance? What is the symbol for resistance?
Material of properties - how much they oppose the flow of electrons through them
Symbol - R
What is resistance measured in?
Ohms ( Ω )
What are materials that have low resistance? (i.e., let electrons flow easily)
Conductors (ex. copper, metals)
What materials have high resistance? (i.e., oppose the flow of electrons)
Insulators (ex. glass, ceramics, wood, paper, plastic)
What is Ohm’s law?
Current through a material is directly proportional to the voltage across it and inversely proportional to the material’s resistance
Equation for Ohm’s law?
I = E / R
Current = Voltage / Resistance
Amps = Volts / Ohms
What is the resistance of a circuit in which a current of 3 amperes flows when connected to 90 volts?
R = E / I
R = 90 (a) / 3 (v)
R = 30 Ω
What is power? What is the symbol?
Power = rate at which electrical energy is used
Symbol - P
What is power measured in?
Watts (W)
In a DC circuit, what is the equation for power?
P = E x I
*in AC circuit, have other considerations
How much power is delivered by a voltage of 13.8 volts DC and a current of 10 amperes?
P = E x I
P = 13.8 (V) x 10 (A)
P = 138 W
