Physics multiple choice exam

Current

current is the flow of charge in a circuit measured in amps (A)

Potential

the amount of energy per unit of charge measured in volts (V)

Energy

can be determined using potential and current measured in joules (J)

Electrical resistance

a measure of the opposition of the flow of current in a circuit

Resistance (definition)

it is defined by Ohm’s law and is measured in units of volts/amps of Ohms (omega symbol)

Resistance (what affects it?)

length, thickness of material, temperature of substance

Power

describes the rate of energy usage, measured in watts (W)

Kirchhoff’s Current law

the current flowing into a node must be equal to the current flowing out of it. (current is the same in series)

Kirchhoff’s Voltage law

the sum of the voltage differences around any closed loop in a circuit must be zero (voltage in parallel is the same)

how do you add resistors in series?

add them together

how do you add resistors in parallel

add the inverses

Magnetic force

similar magnetic poles repel each other with force, even at a distance. dissimilar magnetic forces attract each other with a force, even at a distance

magnetic fields

field lines are always drawn from north to south

Straight Conductor

magnetic fields make a circle around the rod

Solenoid

the magnetic field moves towards the positive charge

Right hand rule #1

thumb in the direction of the current fingers indicating the direction of the magnetic field (straight conductor)

Right hand rule #2

fingers wrap in direction of current thumb indicating the direction of the field (solenoid)

Right hand rule #3

palm points in the direction of the magnetic force, fingers point in the direction of the magnetic field, thumb points in direction of the current

Faraday’s law

it states that any change in the magnetic field near a conductor induces a voltage in the conductor, causing an induced electrical current

Len’s law

if a magnetic field induces a current in a coil, the electric current is in such a direction that it’s own magnetic field opposes the change that produced it

things that cause a higher voltage

a larger magnet strength, number of loops, speed of magnet

things that cause a lower voltage

a larger area of loops

step down transformer

current goes up voltage goes down

step up transformer

current goes down, voltage goes up

characteristics of waves

amplitude, period, wavelength, frequency, speed

transverse waves

moves perpendicular to movement ex: baseball game wave

longitudinal waves

moves parallel to movement ex: sound waves, earthquakes

torsional waves

spins one way then the other ex: swings

what is the speed of a wave dependent on?

the medium it travels through, the speed of a sound wave in air, air temperature

how are sonic booms created?

a barrier is created when moving faster than the speed of sound out of pressure waves, when broken it creates a sonic boom

Mach #

>1 = subsonic, between 1 and 5 = supersonic <5 = hypersonic

what is the Mach # dependent on

air temperature, object speed, speed of sound

Doppler effect

the perceived change in frequency of a sound as it moves towards or away from an observer

Principle of superposition

when waves interact we add their amplitudes to determine the resultant wave

constructive interferance

the process of forming a wave with a larger amplitude when two or more waves combine

destructive interference

the process of forming a wave with a smaller amplitude when two or more waves combine

standing waves

created when waves with the same frequency, velocity and wavelengths interfere

fixed end reflections

when a wave reflects off of a boundary that is more dense it’s reflection is ½ wavelengths out of phase with the original wave

free end reflections

when a wave reflects off of a boundary that is less dense it’s reflections is in phase with the original wave

resonance on strings

number of nodes between fixed ends and overtone are equal to frequency #, harmonic is one more than frequency #, wavelengths is number of total node x 0.5

resonance in tubes (closed end)

harmonic × ¼ is the # of waves, overtone is # of node not on the end

resonance in tubes (open end)

harmonic x ½ is # of waves, overtone is # of nodes - 1

kinematics

the study of motion

Distance

the total length of the path travelled

Position

the location of an object with respect to a reference point

Displacement

the change in an object’s position

Scalar measurements

they have a magnitude and a unit

Vector measurements

they have a magnitude, unit and direction

position time graph slope

the velocity of the object

Acceleration

the change in velocity per unit of time

position time graph for an accelerating object

curved line of motion

slope of tangent to curved line (position-time graph)

instantaneous values of velocity

velocity time graph slope

acceleration

area under the line in a velocity time graph

displacement

straight, horizontal line on velocity time graph

constant velocity, no acceleration

straight upward slope on velocity time graph

increasing velocity, constant positive acceleration(straight horizontal line on acceleration graph)

straight downward slope on velocity time graph

decreasing velocity, constant negative acceleration(straight horizontal line on acceleration graph)

area under acceleration graph

velocity

Projectile

any object that moves along a 2 dimensional trajectory under the influence of gravity only

what angle is a projectile hit at if it goes it’s maximum horizontal displacement

45 degrees

4 fundamental forces

electromagnetic, gravity, weak nuclear, strong nuclear

Newton’s first law

all objects will remain at rest or at a constant velocity until acted upon by an unbalanced force

Newton’s second law

when an unbalanced force is applied to an object, the object will accelerate (F = ma)

Newton’’s third law

for every action force there is an equal opposite reaction

gravity

it acts through the mass of an object

Normal force

it is a part of an action-reaction pair. when an object presses on a surface, the normal force in the reaction force that presses back, it is alway perpendicular to the surface

coefficient of friction

a measure of the attraction between two materials

Friction

depends on the nature of 2 surfaces in contact and the magnitude of the normal force

Energy flow diagrams

Define a system, determine critical instances

Work

the transfer of energy from on form to another

kinetic energy

the energy of motion (Ek = 1/2mv squared)

Gravitational potential energy

stored in an object due to it’s height (Eg = mgh)

elastic potential energy

springs, rubber bands

nuclear potential energy

stored in the nucleus of an atom

electric potential energy

positive and negative charges

magnetic potentila energy

magnetic poles

chemical potential energy

stored in chemical bonds

radient potential energy

stored in light

Law of conservation of energy

energy cannot be created or destroyed only transformed

Efficiency

the completeness of energy transfer, usually expressed as a percent Eout divided by Ein

what type of friction is usually greater?

static friction