science midterm

what are the two types of electrical charges?

positive and negative

what is it called when you have an even number of positive and negative charges?

neutral

what is the law of charges?

opposites attract, likes repeal

a positively changed object has more what than what?

has more positive than negative

a negatively changed object has more what than what?

has more negative then positive

what is the list that ranks objects to take negative charges called?

electrostatic series

triboelectric

is it the top or bottom of the

triboelectric series that take negative charges?

the top of the list takes the negative charges and the bottom of the list loses them

what charge moves?

negative

what is ohm’s law used for?

used to calculate the resistance of a electrical circuit

what is the ohm’s law formula?

R= V/I

explain each symbol in the ohm’s law formula?

R= is the resistance in ohms

V= voltage in volts

I= current intensity in amps

what 2 other thing use the same formula as resistance and are closely linked?

current intensity and potential difference

A circuit has a resistance of 10Ω & a current intensity of 5A.  What is the potential difference?​

V = 50V​

A circuit has a resistance of 20Ω & a potential difference of 100V.  What is the current intensity?​

I= 5 A​

     

A circuit has a potential difference of 16V & a current intensity of 2A.  What is the resistance?​

R= 8 Ω​

where is an Ammeter placed in a circuit?

* In order to measure the **current** traveling through a circuit, an **ammeter** must be inserted into the circuit. ​

what does an ammeter read?

the current intensity of it

in what type of circuit can an ammeter be placed anywhere and read the same current intensity?

In a **series** circuit an ammeter can be placed anywhere along the wire and it will have the **same current intensity** reading.​

will the ammeter read the same anywhere in a parallel circuit?

no

**Which ammeter correctly measures the current flowing through R1?**

**Which ammeter correctly measures the current flowing through R2?**​

**Which ammeter correctly measures the total current?**​​

1. 2
2. 3
3. 1 and 4

what does a voltmeter read?

voltage or potential difference

where is a voltmeter always placed in a parallel?

outside of the circuit

is a series circuit does the voltmeter read the same everywhere?

no it does not

in a parallel circuit will the potential difference/voltmeter read the same along the circuit?

yes

What is the voltage going through V2 if the reading on the  ammeter is 2 amps?​

What is the voltage going through VT if the reading on the  ammeter is 2 amps?​

12v and 40v

what is energy? give 2 examples

energy is the ability to do work. all appliances need energy to work. hair dryer needs to be plugged in to get energy to work​ and a light bulb needs electrical energy to shine bright​.

what is power?

the rate in which power is used. it is the product of potential difference (voltage) and current intensity.

what is the symbol and unit for energy?

E and joules J

what is the symbol and unit for power?

p and watts W

what is the formula for energy?

power times time

A hair dryer has a power rating of 425W & is used for 10 minutes.  How much energy is used?​

255,000 Joules of energy were used to work the hair dryer​

what is the formula for power?

p=v times I

An appliance requires 120V & 12A to work.  It is used for 900 seconds.  How much energy is used?​

P = 1440 W ​ and energy =1,296,000 J​

how do you calculate cost? what units

cost= cost of electricity times power(kw) times time(hours)

how many watts make up 1 kw?

1000w

A 3.9 kilowatts curling iron is used for 10 minutes once a day. Electricity costs $0.05/kW•h. How much does it cost to use this curling iron for a week?​

cost= $0.23

very electrical appliance has what? what does that do?

**rating plate. gives us the info so we can calculate the cost**

what is the unit ***ampere?***

a quantity of charges per time​

what is the unit volt?

energy per unit charge​

what are all the units for energy?

Joules​

W•s​

kw•h​

V•A•s​

what are the units for power?

watts and kw

A circuit has a resistance of 10Ω & a current intensity of 5A.  What is the potential difference?​

V=50v

A circuit has a resistance of 20Ω & a potential difference of 100V.  What is the current intensity?​

5A

​what is a circuit?

it is made up of a power supply, connecting wires and various elements that allow electrons to leave the power source travel through the elements and back to the power source.

what are the 2 types of circuits? what is the difference?

series pen has to follow wire and parallel pen can go in different directions

what is Equivalent Resistance?

the total resistance of the circuit.

what is the formula for Req (equivalent resistance) for series and parallel?

**Series –** ***Req = R1 + R2 + R3***​

parallel - 1/req= 1/R1 + 1/R2 + 1/R3

what is current intensity?

what is __***A***__***mpere?***

what is an ammeter?

1. the rate of flow of **electrons** through a wire.​
2. coulomb of electrons per second
3. *the instrument used to measure current intensity*

what is potential difference?

what are volts?

what is a voltmeter used for?

1. energetic force  that **causes electrons** **to flow**

​ 2. joule per coulomb of electrons​. Provided by a battery or power supply


3. used to measure potential difference​

what is conductance?

**how easily current flows** through a wire.​

formula for conductance?

G= I/V

what is the unit and symbol for conductance?

Units = Siemens​ Symbol = G ​ Conductance of 1S = 1 amp per volt​

hat is the conductance of a circuit with a current intensity of 20A & a potential difference of 5V?​

4s

how do you solve conductance on a graph?

***G =* __*∆I (I*__*2*__*– I*__*1*__*)*__**​

       ***∆V (V2-V1)***​ use this formula and plug in your 2 points

what is resistance? what is a resistor used for?

how **difficult** it is for current to flow . Resistance is the opposite of conductance. to slow current down.

resistor has? conductor has?

1. high resistance & ​low conductance​
2. low resistance & ​high conductance​

what phenomenon has been used to create electromagnets?

Whenever electricity flows through a wire, a magnetic field is created.​

what are the 2 types of conductors that form a magnetic filed from the flow of electrons.

“straight-line” conductor (an uncoiled wire)​ or a solenoid or a coil​ (coiled wire)

give info on solenoids

wire rapped around core (tube), they have a current flowing through them, have a magnetic filed, magnetic filed looks like the one of a bar magnet.

what is a core? what influence the strength of the electromagnet? what are some metals that can be used for a core? why is iron used the most and not metals like steal?

1. is the object that is inserted into the solenoid, creating an electromagnet.​
2. different materials
3. iron, steel, nickel or cobalt
4. because when you turn off the electricity it demagnetizes.​
5. Metals like steel remain magnetized thus creating a permanent magnet. ​

what are some Factors that affect the Magnetic field of an Electromagnet?

the core metal= ferromagnetic core will increase the strength of the magnetic field​

the current intensity= higher current stronger the magnetic field

number of loops/number of turns= more loops strong field

what are some good metals for cores?

**Ferromagnetic cores** strengthen the magnetic field​ Steel, nickel & cobalt​ Iron is a VERY GOOD core​.

Wood, plastic and aluminum cores do not increase the strength of the magnetic filed.​

To find the strength of the electromagnet scientists use what formula?

F=IN

electromagnet formula what does f n and i stand for?

* ***F*** is force or strength of the electromagnet​
* ***I*** is the current intensity traveling through the wire​
* ***N*** is the number of loops around the core​

explain the Solenoid Rules Right Hand Rule​

1. Place palm of right hand on positive end.​
2. At the positive end, look to see if the wire is in front or behind the middle tube.​
3. If the wire is in front of the tube at the positive end, place your hand on top of the core. If the wire is behind the tube at the positive end, place your hand under the tube.​
4. Double check both palm and fingers.​
5. Thumb points towards North.  The other end is South.​

\

where does the needle on the compass point to?

**needle is North** and is attracted to **South.**​

what to do When the **+** and the **–** are not given on a diagram

remember that the longer line on the battery is always positive.​

explain the Straight Line Conductor  ​ \n Right Hand Rule​

1. Using your right hand, point your thumb towards the **negative** post​ hand behind the conductor As long as the thumb points to​

negative​
2. With your hand open, your finger nails are South and your knuckles are North.​
3. If your hand is behind the wire and you cannot see your finger nails, close your hand.​ **Knuckles are up (N)**​

**Nails are down (S)** 

what are the 3 types of magnets?

magnet, Ferromagnetic and non-magnet

what is a Ferromagnetic?

is attracted by a magnet, can be magnetized, Most common ferromagnetic substances are **iron**, **nickel** and **cobalt**​.

what is a non magnet?

* Is not attracted by a magnet​
* Example: glass, plastic, wood, and most metals​

what are the lines around the magnet called give the rules

force that have direction and strength ***magnetic field.***

the **lines never cross**​

* they always go from **North to South**​
* the **closer** the lines, the **stronger** the attraction​

what are the 2 types of chemical changes?

physical and chemical

what is a physical change?

it does not change the chemical composition or the nature of the substance. easily reversible. (The substance is still there it only changes the way it appears.)​

what are some key words that tell you a physical change has accord?

* Crush/Pulverize​
* Melt​
* Evaporation​
* Condensation​
* Sublimation​
* Solidification​
* Dissolve​​

what are chemical changes?

changes the chemical composition or make up of the substance. new substances are formed with new properties. not easily reversed Reversible only through chemical means or reactions

what are some signs of a chemical change?

formation of a gas, formation of a precipitate, change in color, production heat and or light and increase or decrease in mass.

what do chemical equations consist of what?

reactants and products

what is the law of conservation of mass?

in a chemical reaction mass is neither created nor destroyed.

In a chemical reaction below, how many grams of oxygen (O2) was used given the following information.​

O2 = 107 grams​

37 grams sulphuric acid (H2SO4) is neutralized with calcium hydroxide (Ca(OH)2). ​

  During the reaction, calcium sulphate (CaSO4), a salt, and water are produced.  If 14g of water & 51g of salt are produced, how much calcium hydroxide was initially used?​

**Ca(OH)2 = 28 grams**​

what is the formula for the conservation of matter?

MASS OF REACTANTS = MASS OF PRODUCTS​

what are nuclear transformations?

affect the nucleus of the atom where it splits to form new elements.  The particles are rearranged.​

what are the two types of chemical changes?

oxidation and combustion

what does s, l, g, aq?

solid, liquid, gas and aqueous

what is oxidation?

* Many substances oxidize when they __react with the oxygen in the air or a substance with similar properties to oxygen.__​
* __Combustion is a form of oxidation that releases a large amount of energy.__​
* Presence of air, light, water and salt can accelerate oxidation
* rust is a form of oxidation

what are ways to slow/prevent oxidation?

* Galvanize the metal (coat in Zinc)​
* Oil coating​
* Rust proofing​
* Water proofing​
* Add preservatives to food which may oxidize​

what is combustion?

a form of oxidation that releases a large amount of energy. some examples are Burning wood, cellular respiration, Burning fossil fuels​, Principle of the “internal combustion engine”.​

what are the 3 types of combustion?

rapid, spontaneous and slow

what is rapid combustion? examples

spectacular and in a short time. it releases a lot of energy in the form of heat or light. ex. candle, log fire, explosion, car engine

what is spontaneous combustion? examples

rapid and without energy from outside sources it unpredictable. ex. dry wood catches fire by itself, hay heats up, some forest fires, oil coated rags

what is slow combustion? examples

occurs over a long period of time and energy is released gradually into the environment. ex. decomposition, fermentation, cellular respiration, metal corrosion

what are the 3 conditions to promote combustion?

1. fuel something to burn such as wood, propane, oil and gas.
2. oxidation agent it causes the fuel to react such as oxygen in the air that’s most common.
3. ignition temperature that’s the minimum temp that combustion starts. its different for each type of fuel.

what is the fire triangle?

its a triangle with the 3 conditions. heat on top then oxygen and fuel.

liquid to solid

freezing or solidification

solid to liquid

melting

solid to gas

sublimation

gas to solid

deposition

gas to liquid

condensation

liquid to gas

evaporation