Understanding Electricity - High School Physics
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A current of 
flow in a wire. How many electrons are flowing past any point in the wire per second?
A current of 
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.
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.
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What is the maximum power consumption of 
portable CD player that draw a maximum of 
of current?
What is the maximum power consumption of 
The power in a circuit is equal to the current times the voltage.
The power in a circuit is equal to the current times the voltage.
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The direction of conventional current is taken to be the direction that __________________ .
The direction of conventional current is taken to be the direction that __________________ .
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.
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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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
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
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.
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.
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If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit
If the resistance in a constant voltage circuit is doubled, the power dissipated by that circuit
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.
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
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.
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Why might a circuit breaker open if you plug too many electrical devices into a single circuit?
Why might a circuit breaker open if you plug too many electrical devices into a single circuit?
When plugin objects into a single circuit, these objects are connected in parallel as each one will receive the 120V from the electrical outlet. However, as additional objects are added, the current is thereby increased. Circuit breakers are designed to trip once the current reaches a maximum load and shuts down the circuit to protect the wires, and the devices that are plugged into the circuit as high current can damage these devices.
When plugin objects into a single circuit, these objects are connected in parallel as each one will receive the 120V from the electrical outlet. However, as additional objects are added, the current is thereby increased. Circuit breakers are designed to trip once the current reaches a maximum load and shuts down the circuit to protect the wires, and the devices that are plugged into the circuit as high current can damage these devices.
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A 4.5V battery is connected to a bulb whose resistance is 
. How many electrons leave the battery per minute?
A 4.5V battery is connected to a bulb whose resistance is 
We first need to determine the current coming through the bulb. We can use Ohm’s law to determine this.
Current by definition is the amount of charge per unit time.
We are looking at the number of electrons in one minute which is 60 seconds.
We now know the amount of charge passing through in 60 seconds. We know that the charge of the electron is 
. We can use this to figure out how many electrons are going through.
We first need to determine the current coming through the bulb. We can use Ohm’s law to determine this.
Current by definition is the amount of charge per unit time.
We are looking at the number of electrons in one minute which is 60 seconds.
We now know the amount of charge passing through in 60 seconds. We know that the charge of the electron is 
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Nothing happens when birds land on a power line, yet we are warned not to touch a power line with a ladder. What is the difference?
Nothing happens when birds land on a power line, yet we are warned not to touch a power line with a ladder. What is the difference?
Electricity travels from the point of highest potential to the lowest potential. We measure the difference between these two potentials as the voltage. Since both of the birds' feet are on the wire, both feet have the same potential. However, if the ladder touches the power line and the bottom of the ladder is on the ground, there is a much higher potential difference (as the ground is at 0 potential). Therefore the electricity will travel down the ladder!
Electricity travels from the point of highest potential to the lowest potential. We measure the difference between these two potentials as the voltage. Since both of the birds' feet are on the wire, both feet have the same potential. However, if the ladder touches the power line and the bottom of the ladder is on the ground, there is a much higher potential difference (as the ground is at 0 potential). Therefore the electricity will travel down the ladder!
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When a light switch is turned on, the light comes on immediately because
When a light switch is turned on, the light comes on immediately because
It's kind of like when you turn on the faucet; the water doesn't have to travel from the water tower to your house before it starts flowing. Similarly, the electrons are always in the circuit. Once the switch is turned on, there is a voltage difference present, which is what then pushes these electrons through the circuit (like turning on the faucet).
It's kind of like when you turn on the faucet; the water doesn't have to travel from the water tower to your house before it starts flowing. Similarly, the electrons are always in the circuit. Once the switch is turned on, there is a voltage difference present, which is what then pushes these electrons through the circuit (like turning on the faucet).
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