Current Electricity

Static electricity vs current electricity

Static electricity has charges built up in one location and current electricity have electrons on the move.

How is energy created

Friction: Energy produced by rubbing two material together.
Heat: Energy produced by heating the unction where two unlike metals are joined.
Light: Energy produced by light being absorbed by photoelectric cells.
Chemical: Energy produced by chemical reaction in a voltaic cell.
Pressure: Energy produced by compressing or decompressing specific crystals.
Magnetism: Energy produced in a conductor that cuts or is cut by magnetic lines of force

electrochemical cell, battery, electrodes

Electrochemical Cells: a portable device that
converts chemical energy to electrical energy
Two electrodes (positive and negative) in an
electrolyte (conducting solution)
Electrodes are conductors
Electrons flow from one electrode to the
other
Battery: two or more electric cells together

anode to cathode

in any voltaic cell, electrons flow from the anode (positive) to the cathode (negative). Ex. copper electrode (anode) and zinc electrode (cathode)

What are electrolytes?

A solution that conducts electricity because it contains ions. Ex. dilute sulphuric acid

wet cell and dry cell

Wet Cell: electrolyte is liquid
Dry Cell: electrolyte is paste

Fuel Cell

An electrical-chemical device that converts fuel, such as hydrogen, into an electrical current.

Direct Current (DC)

Electric current that flows in only one direction

Alternating Current (AC)

A flow of electric charge that regularly reverses its direction.

DC vs AC

In direct current, the voltage is always constant, and the electricity flows in a certain direction. In contrast, in alternating current, the voltage periodically changes from positive to negative and from negative to positive, and the direction of the current also periodically changes accordingly.

How do electrons transfer energy?

Electrons repel one another. When one electron moves, it pushes another.

Mechanical Kinetic Energy

Energy due to an object's motion. If object has more kinetic energy it moves faster.

turbine generator

a moving fluid (water, steam, gases, or air) rotates a series of blades mounted on a rotor shaft which rotates the rotor shaft which is attached to an electromagnet

Faraday's Law

An electric field is induced in any region of space in which a magnetic field is changing with time. Faraday's Law states that changing magnetic fluxes through coiled wires generate electricity which is how turbine generators generate electricity.

What do fuses and breakers do?

Circuit breakers or fuses are connected in series with circuits leading to outlets in your home. If there is too much current, the breaker will trip or the fuse will blow.

How much amperes are needed to be painful/lethal?

any amount of current over 10 milliamps
(0.01A) is capable of producing painful to
severe shock
currents between 100 and 200 mA are lethal.

What are watts?

Power is measured in watts
Power = Energy/time
1 Watt = 1 J per second (1 J/s)
Watts can also be calculated as (Voltage (V) x Current (I))

How do you calculate energy?

Voltage (V) x Current (I) x time (s)

Measured in Joules

How much is a kilowatt? A gigawatt?

KiloW=1000W
GigaW=1,000,000W
The kilowatt◦hour (kW◦h) is the unit for
energy usage

Incandescent vs Fluorescent

A 100W incandescent bulb uses about 40
kW◦h. A 25W compact fluorescent light bulb only uses 10 kW◦h Therefore, the CFL is more efficient because it converts a higher percentage of electrical energy into light than an incandescent bulb

When is energy most expensive?

Energy is more expensive during peak hours
(9am-5pm) when the demand for energy is at
the highest

How do you calculate the percent efficiency?

(energy out/energy in) X 100

How do you calculate cost of electricity?

Power used (kW = 1000W) x time (h) x cost rate (kWh)

Measuring current

Electric current is measured in amps (A) using an ammeter connected in series in the circuit. Measured using an ammeter Unit: Ampere (A) Placed in series
The symbol I is used

Measuring voltage

Difference in electric potential energy per unit charge measured at two different points
Unit: Volts (V)
Placed in Parallel

Measuring resistance

The ability of a material to oppose the flow of electric current. Measured in ohms (Ω)
Ohmmeter: measures resistance
Connected in parallel with a load

Series circuit

A circuit in which all parts are connected end to end to provide a single path of current.

Parallel circuit

A closed electrical circuit in which the current is divided into two or more paths and then returns via a common path to complete the circuit.

How is current, voltage, and resistance calculated in series?

Current: CONSTANT --> iT = i1 = i2
Voltage: SUM --> VT = V1 + V2
Resistance: SUM --> RT = R1 + R2

How is current, voltage, and resistance calculated in parallel?

Current: SUM --> iT = i1 + i2
Voltage: CONSTANT --> VT = V1 = V2
Resistance: INVERSE SUM --> 1/RT = 1/R1 + 1/R2

Factors that affect resistance

1. TYPE OF MATERIAL (insulator vs. conductor)

2. CROSS-SECTIONAL AREA (thicker = less internal resistance/more room to move)

3. LENGTH (Increase Length = Increase internal resistance. Travelling through more material)

4. TEMPERATURE (Wire gets warmer, atoms of the wire gain energy & vibrate faster Causes more collisions with electrons in current = increased resistance)

What is Ohm's Law?

V=IR

What happens to lightbulbs when there is higher resistance in PARALLEL?

The voltage always stays the same, and current can vary. Thus, it decides the brightness and since current is V/R. Higher resistance means a lower current since if R is larger the quotient is smaller. So higher resistance in parallel circuits makes the lightbulbs dimmer.

What happens to lightbulbs when there is higher resistance in SERIES?

The current is all the same so voltage decides what is brighter and since voltage is I*R higher resistance is a higher voltage since if R is larger the result is larger. So higher resistance in series circuits makes the lightbulbs brighter.

express conservation of charge and energy/the table

kirchoff's law

What happens when more lightbulbs are added to a series circuit? In a parallel circuit?

Increasing the number of bulbs in a series circuit decreases the brightness of the bulbs. In a series circuit, the voltage is equally distributed among all of the bulbs. Bulbs in parallel are brighter than bulbs in series. In a parallel circuit the voltage for each bulb is the same as the voltage in the circuit. In parallel circuit they stay the same.

Voltage drop across circuit elements (series)

(loss of energy per charge)