physics help homework?

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the ones with the stars are the ones that i think are right..
but im not sure..please put the right answer :) tanx






1.If the coolant in an air conditioner has a lower temperature than the air in a building, then ____.
A.heat will flow from the air into the coolant-
B.heat will flow from the coolant into the air
C.heat will flow from the coolant into the air




2.You have two pieces of wire that allow electrons to pass through them when they are connected to each other. If you insert a piece of rubber between the wires, the electrons do not flow. The rubber material is ______.
A.Circuit
B.conductor
C.fuse
D.insulator*

In order for a person to "see" an object, light waves pass through the ___________.

A.cornea
B.iris*
C.lens
D.Retina


2.Which best describes longitudinal waves

A.Compressions and rarefactions make up longitudinal waves, which can only travel in matter.*

B.Light energy travels in longitudinal waves and can travel in either matter or empty space.

C.Longitudinal waves carry sound energy and are made up of crests and troughs.


Which waves cause matter to move back and forth in the same direction?
A.Transverse waves*
B.magnetic
C.longetudinal

Which happens to the magnetic field of a wire when you change the direction of the current in the wire?
A.Becomes stonger
B.It becomes weaker.
C.It changes direction too.*
D.It stays the same.


When a wire is made smaller, the resistance increases. Which happens to the electric current?

A.Decreases*
B.increases
C.stays the same

Light from the sun travels through space to Earth's atmosphere. Which will light waves do when they move from empty space into matter made up of different gases?

A.move at the same speed
B.move faster as they transmit
C.slow down and refract
D.speed up and reflect*


A clock radio is rated as 30 W of power output. If the radio also draws 30 W at 120 V, which will the current draw be
A.0.25 A*
B.4 A
C.3,600 A
D.0.5 A

If amplitude of the waves coming from a light bulb decreased, which would you expect to happen?
A.The brightness of the bulb would decrease.*
B.The intensity of the light would increase.
C.The light waves would travel faster


All of the following are examples of chemical energy except _______.
A.burning a candle
B.coasting downhill on a bike
C.working muscles using food*

Energy that flows from an object with a higher temperature to an object with a lower temperature is ______.
A.thermal energy
B.temperature*
C.heat energy

What is happening if energy input remains constant and voltage remains the same in a circuit, but the current decreases?
a.The resistance has increased.*
b.The volts have decreased.
C.The power has increased.


You wrap a wire around a piece of iron. If you slowly increase the strength of an electric current flowing through the wire, you would expect _____.

A.the magnet to become stronger*
B.the magnet to stop producing a field
C.the wire to move
D.the wire to unwrap

What type of energy is sound?

A.electromagnetic energy
B.kinetic energy *
C.mechanical energy
D.potential energy

All of the following are examples of electric current except

A.charges flowing in one direction through a circuit
B.charges moving through a conductor
C.electrical discharge from a charged object
D.electrons moving through a copper wire

A toaster draws 8 A of current with a voltage of 120 V. Which is the power used by the toaster?
A.960 W

Which sets of data show a wave with the shortest wavelength?
A.speed = 100 million m/s and frequency = 50 million Hz*
B.speed = 150 million m/s and frequency = 1500 Hz
C.speed = 300 million m/s and frequency = 100 Hz


A toy boat is floating in a large metal bucket. If you build a fire under the bucket, how the heat will transfer from the fire to the boat?
A.Water molecules in the bucket will transfer the heat.*
B.Metal molecules of the bucket will transfer the heat.
C.Surrounding air molecules will transfer the heat.


Lighting a match results in light and heat. Since energy was not created by the match, what transformation took place?
A.Friction generated heat to release chemical energy.
B.Light energy was generated from radiant energy.*
C.Sound energy generated heat energy.

Answer
1.A
2.D
--- C and A (go with C)
2.A
--A
--C
--A
--C
--A
--A
--B
What is happening if energy input remains constant and voltage remains the same in a circuit, but the current decreases?
a.The resistance has increased.*
b.The volts have decreased.
C.The power has increased.
This is a trick question since P=IV = IR^2 the current can't decrease without the energy input decreasing if the voltage is constant. Answer a is best but energy input will decrease also.

--A
--B (also C)
--C.electrical discharge from a charged object
--A.960 W
--A.speed = 100 million m/s and frequency = 50 million Hz*
--A.Water molecules in the bucket will transfer the heat.*
--A.Friction generated heat to release chemical energy.

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