physics flashcards term 2 finals gr11b REVIEW PPTS BEFORE STUDYING THIS

capacitor

energy can be stored in an electric field, this is a device for storing electrical energy, theyre used in computers, televisions, and digital cams

what is the effect of increasing the surface area of the plates on the capacitor

the capacitance increases as the area increases (directly proportional)

what is the effect of decreasing the separation between the plates of a capacitor ?

the capacitance increases as the distance between the plates decreases (inversely proportional)

capacitance formula

C = q / delta V

measured in farads (F) where 1 F =1 C/V

q is the charge and V is the potential difference

what values of capacitance are mostly used

1 F is a large amount of net charge, most capacitors have capacitances between 10 picofarads (10 × 10^-12 F) and 500 microfarads (500 × 10^-6 F)

however memory capacitors have capacitances from 0.5F to 1F to prevent memory loss of device

how are electric currents produced

when two conductors touch, charges flow from the conductor at a higher potential to the ne at a lower potential, until there is no potential difference between the two conductors

electric current

a flow of charged particles

direction of electric current and flow of electrons

the direction in which a positive test charge would move

the charges that flow are actually negatively charged electrons, as a result, the flow of electrons and the current arrow point in opposite directions

the more the charge that flows, the faster it flows, the greater the electric current

electric current formula

I = delta q / delta t

q » charge

t » time

measured in ampere (A) or coloumbs per second (C/S)

electric circuit

when charge flows through a closed path and returns to its starting point

types of electric circuits : DC circuit / direct-current circuit

the current always flows in the same direction. circuits that run on batteries are typically this type of circuit

types of electric circuits : AC circuit / active-current circuit

circuits with currents that periodically reverse their direction, ex. the electricity provided by a wall plug in your house

whats needed for electrons to flow in a circuit

it needs an external energy source (ex. a battery)

how can a abttery provide to be an external energy source for a circuit

a battery uses chemical reactions to produce a difference in electric potential between its two ends, referred to as terminals

a battery’s positive terminal has a high electrical potential and is denoted with a + sign, the negative terminal has a low electrical potential and is denoted with a - sign

what happens when a battery is connected to a circuit

electrons move in a closed path from one terminal of the battery through the circuit and back to the other terminal of the battery

the electrons leave from the negative terminal of the battery and return to the positive terminal

electromotive force / emf

the difference in electric potential between the terminals of the battery, represented by the greek letter epsilon (fancy looking E) its the same unit as volt basically lol

ohms law

applied voltage = current X resistance

V = IR

si unit » volt (V)

resistance

R = delta V / I

essentially rearrange ohms law to get this formula ^^

measured in ohms

how can we tell if a device obeys ohms law ?

a device having constant resistance independent of the potential difference is said to obey it

most metallic conductors obey it, at least over a limited range of voltages

transistors and diodes do not obey ohms law

resistor

a device designed to have a specific resistance, could be made of graphite, semiconductors, or long and thin wires

semiconductors

there are 2 types

• n-type : current is carried by negative electrons

• p-type : current is carried by positive electrons

unlike a typical resistor, a semiconductor has a lower resistance when its temperature increases

diodes

uses p-type semiconductors joined to an n-type semiconductor, it allows current to flow in 1 direction but not the other

forward based diode

when the positive terminal of a battery is attached to the p-type semiconductor in an ideal diode, the current flows with 0 resistance

reverse based diode

if the positive terminal of a battery is connected to the n-type semiconductor of a diode, no current flows at all

applications of diodes

the conversion of AC current (which alternates in direction) to DC current

the operation of an LED, light-emitting diode

transistor

a “sandwich” of 3 layers of semiconductors

most common type of transistor has an n-type semiconductor on either side of the transistor and a p-type semiconductor in the middle (known as npn transistor)

transistors van also be made with the opposite sequence of semi conductors (pnp transistor)

basic function of a transistor is to act as an electronic switch that controls the flow of current in a circuit

series circuits

electric circuits often connect many resistors in various ways, series circuits have resistors connected end to end, a connection with only 1 current path

equivalent resistance for resistors in series

Req = R1 + R2 + R3 + …

SI unit » ohm

current value in series circuits

I totally = I1 = I2 = I3 = …

voltage in series circuits

V total = V1 + V2 + V3 + …

parallel circuits

resistors that are connected across the same potential difference are said to form this circuit, the current has two or more paths to follow

equivalent resistance for resistors in parallel

1 / Req = 1 / R1 + 1 / R2 + 1 / R 3 + …

si unit » ohm

voltage in parallel circuits

V total = V1 = V2 = V3 = …

current in parallel circuits

I totally = I1 + I2 + I3 + …

ammeter

the device used to measure current, It’s always connected in series with the circuit so it can measure all the current passing through.

voltmeter

A voltmeter measures the voltage (potential difference) between two points in a circuit.

Explanation:

It’s connected in parallel to the component you’re measuring. It tells you how much energy per charge is being used or supplied (in volts, V).

multimeter

sometimes the functions of an ammeter, voltmeter, and ohmmeter (device used to measure resistance) are combined to make this device

power formula

power = current X voltage

P = IV

si unit » watt W