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Electric Current

rate fo flow of electric charge

Ampere

One ampere is the amount of current flowing in each of two infinitely-long parallel wires of negligible cross-sectional area separated by a distance of one meter in a vacuum that results in a force of exactly 2*10^-7 N per meter of length of wire.

Current

Current is defined in terms of the force per unit length between parallel current-carrying conductors.

Closed Circuit

complete pathway for current

Open Circuit

incomplete pathway for current

break in circuit

infinite resistance

break in circuit

infinite resistance

Short Circuit

Circuit with little to no resistance - extremely high current overheating

Resistance

ratio of potential difference applied across a piece of material to the current through the material

Power

energy per unit time

Ammeter

measures currents

Placement of Ammeter

must be placed in series to allow current to flow through it

Ideal Ammeter

has zero resistance so it will not affect current flowing through

Voltmeter

measures potential difference

Placement of Voltmeter

must be placed in parallel to measure potential difference between two points circuit does not to be broken

Ideal Voltmeter

has infinite resistance so it will not allow any current to flow through it and disrupt circuit

Potential Divider

resistors in series act as 'potential divider'. they split the potential of the source between them.

Light-Dependent Resistor (LDR)

Light Sensor

Light Sensor

a photo-conductive cell made of semiconducting material whose resistance decreases as the intensity of the incident light increases

Negative Temperature Coefficient (NTC) Thermistor

Temperature Sensor

Temperature Sensor

a sensor made of semiconducting material whose resistance decreases as its temperature increases

Strain Gauge

Force Sensor

Force Sensor

a long thin metal wire whose resistance increases as it is stretched since it becomes longer and thinner

Resistance

ratio of potential difference applied across a piece of material to the current through the material

Ohm's Law

for a conductor at constant temperature, the current flowing through ti is proportional to the potential difference across it

Ohmic Device

a device that obeys Ohm's law for a wide range of potential differences (a device with constant resistance)

Non-Ohmic Device

a device that does not obey Ohm's law (resistance is not constant)

Potentiometer

a tie of variable resistor with three contact points (use as a potential divider)

Electromotive Force (emf)

total energy per unit charge supplied by the battery

Terminal Voltage

potential difference across the terminals of the battery

Ideal Behavior

terminal voltage always equals emf since no internal resistance