High School Physics : Electricity

Study concepts, example questions & explanations for High School Physics

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Example Questions

Example Question #1 : Electricity

What is the maximum power consumption of  portable CD player that draw a maximum of  of current?

Possible Answers:

Correct answer:

Explanation:

The power in a circuit is equal to the current times the voltage.

 

Example Question #1 : Electricity

The total amount of charge that passes through a wire’s full cross section at any point per unit of time is referred to as

 

Possible Answers:

Wattage

Electric potential

Current

Voltage

Correct answer:

Current

Explanation:

Current is defined as the amount of charge that passes through a specific area of a wire in a specific interval of time.  It is measured in Amps which are Coulombs per second.

Example Question #4 : Electricity

If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit

Possible Answers:

Decrease to one fourth its original value

Decrease to one half its original value

Increase by a factor of four

Increase by a factor of two

Correct answer:

Decrease to one half its original value

Explanation:

Decrease to one half its original value

 

The equation for Power is 

 

 

According to Ohm’s Law

 

 

We can rearrange this equation for current as this is what is changing in our circuit.

 

 

We can then substitute this back into the power equation.

 

 

 

If we have the original value

  and our second value

 

We can rearrange both for the voltage and set them equal to each other

 

 

 

We know that

 

So we can substitute this value in

 

 

And solve for 

 

 

Therefore the power would be cut in half.

 

Example Question #5 : Electricity

A current of  flow in a wire.  How many electrons are flowing past any point in the wire per second? 

Possible Answers:

Correct answer:

Explanation:

The current is a measure of the amount of charge that passes a given point in a certain amount of time.

 

 

To determine how many electrons are passing this point we need to look at the charge of 1 electron and do a conversion.

 

Example Question #1 : Electricity

The direction of conventional current is taken to be the direction that __________________ .

Possible Answers:

negative charges would flow

positive charges would flow

Correct answer:

positive charges would flow

Explanation:

We often think of current flowing from the top of the battery to the bottom of the battery.  The top of the battery has a higher electrical potential than the bottom of the battery and is associated as being positive.  Charges interact in such a way where like charges repel and opposite charges attract.  Since we think of the charges traveling away from the positive end of the battery and toward the negative end of the battery, this would model the motion of a positive charge (away from positive and toward negative).  Since it is not protons that move through the circuit, but rather electrons.  It is more accurate to describe the flow of electrons from the negative side of the battery to the positive side.

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