Unit 5: Currents, Circuits, and Magnetism Flashcards
battery
an energy storage device that provides a constant potential difference (6V) between two locations (terminals) inside the battery
Current (I)
the flow of electric charge
convention system for current refers to positive charge, moving
Which way do electrons travel in a battery?
positive terminal to the negative (opposite of usual)
How does a battery work?
- voltage is created when positive and negative charges are separated.
- batteries are charged escalators that move positive charge from the negative terminal to the positive terminal
- ## the battery is a source of voltage because the chemical reactions give potential energy to charge
Drift Velocity
electrons move slowly in the direction opposite of the electric field.
Direct Current (DC)
charge that moves in one direction only (battery)
Alternating Current (AC)
the voltage alternates from positive to negative so the output current from the generator changes its direction at regular intervals
- Charge that repeatedly reverses direction
Resistance (R)
the opposition to motion of charge (current) through a conductor
Factors that affect resistance (4)
-cross-sectional area
-material
-temperature
-length
Greater area/ thicker, (less/more) resistance
less resistance
copper, (less/more) resistance
less resistance
Iron, (less/more) resistance
more resistance
low temperature, (less/more) resistance
less resistance
high temperature, (less/more) resistance
more resistance
shorter wire length, (less/more) resistance
less resistance
longer wire length, (less/more) resistance
more resistance
Electric Power (P)
the rate at which electrical energy is converted into non electrical forces of energy like heat or light
(rate at which work is done)
-also known as wattage.
Electric Circuit
path through which charges can flow (bulbs, wires, resistors, batteries)
Open Circuit
no complete path -> no charge flow -> no current
Short Circuit
circuit with no load (no resistors, only wires) so very little resistance, or when an element is cut out of a circuit
Series Circuit
When multiple components are connected in a single loop so all charge must follow a single path
Series Equations
Itotal = I1 = I2 = I3 = …
Vbatt = V1 + V2 + V3 + …
Req = R1 + R2 + R3
Complex Circuit
a combination of resistors within a circuit that includes both series and parallel arrangements
The Req of a SERIES circuit is (smaller/larger) than the largest resistance in the circuit
larger Equivalent Resistance
The Req of a PARALLEL circuit is (smaller/larger) than the smallest resistance in the circuit
smaller Equivalent Resistance
Where in a PARALLEL circuit is there the most current?
where there is the least resistance
Where in a SERIES circuit is there the most current?
current is the same everywhere in the circuit
Parallel Circuit Equations
It = I1 + I2 + I3 + …
Vbatt = V1 = V2 = V3 = …
Req = 1/R1 + 1/R2 + 1/R3 …
Magnetism
derived from electrons spinning on their axis; a charge in motion, which produces a magnetic field
Magnetic domains
strong interaction between neighboring atoms to form large groups that have aligned fields
-unmagnetized materials have domains randomly oriented, with electrons in pairs going opposite directions
How to demagnetize a material
- hammering the magnet
- heat or cool the magnet
this upsets the magnetic domain and repositions the electrons
Magnetic Field
a region in which a magnetic force is detected
-produced by the motion of electric charges
-compass needle will align with the magnetic field lines
Earth’s Magnetic Field
earth’s north is opposite to the geographic
- it’s generated by the movement of charges in the convection current
- it reverses often
Solenoid
A long round coil of insulated wire
- acts like a bar magnet when carrying current
- magnetic field strength is proportional to the number of coils per length
- more coils, stronger fields
Electromagnet
A solenoid with an iron rod through the center increasing the magnetic field; magnetized through circuits
Electromagnetic induction
The process of induction of a current in a circuit without the power supply by changing the magnetic field that passes through the circuit
- magnet or circuit must be moving
- the separation of charges by the magnetic field induces a voltage
Motors
Consist of a coil of wire between two magnets
- current is supplied to the loop by the battery and the magnetic force on the loop causes it to rotate
- converts electrical energy to mechanical energy
Generators
Induces current by changing the orientation of the loop with respect to the magnetic field
- convert mechanical energy to electrical energy
Transformers
Change a small alternating current applied voltage to a large voltage and vice versa
Electromagnetic wave
Composed of oscillating electric and magnetic field that regenerate each other
- produced by accelerating charges
in a typical/conventional electric circuit, electrical current is the flow of
Positive charge
V (Volt) Unit break down
J/C
A (Ampere) Unit break down
C/s
O (Ohm) Unit break down
Js/C²
Which has the greatest electrical resistance?
Dry skin, skin wet with tap water, skin wet with salty water
Dry skin
A bird can perch harmlessly on bear high voltage wires because
All parts of the bird are at the same potential
To prevent shock from occurring when touching an electrical appliance, the outside of the appliance is connected to the
ground
A 50 ohm light bulb and a 100 ohm light bulb are connected in SERIES. Which is brighter?
the 100 ohm light bulb
A 50 ohm light bulb and a 100 ohm light bulb are connected in PARALLEL. Which is brighter?
The 50-ohm light bulb
