Current Flow, Voltage, Resistance:

Examples of 2 ways a light bulb will light when connected to a battery.

Requirements or conditions needed for the bulb to light up:

In a simple circuit:

• battery gives energy to the bulb
• bulb using up energy
• a wire is needed to go back from the bulb to the battery 
• needs a continual flow of charge
• equilibrium of charges

Hydroelectric Plant:

• water at high elevation travels through a penstock to a turbine at lower elevation
• the penstock provides the water that turns the shaft of the generator

Voltage determines the PE.

Current measures how many charges flow through the bulb each second.

Power measures the amount of energy delivered to and radiated by the bulb as heat and light every second. 

The direction of the current flows from positive to negative as shown below. The current must pass through the bulb and out back to the negative side of the battery.

In class, the professor brought out an electroscope. 

These are used to test the presence of charge. They are made of conducting materials. (the findings are listed in the image).

 

In order to measure the current flowing through a part of a simple circuit with one battery and bulb, we had to insert the ammeter at the point of interest. 

*measured in amperes or milliamperes

The current measured was 106 mA  and it was positive.

When the leads were reversed, the current remained the same. 

Here we learned about the relationship between the applied voltage across a resistor and the current through the resistor. 

Apparatus of voltage source connected to a resistor and ammeter:

 The graphs above depict the linear relationship between voltage and current.

The measurements below were used to create a ratio of resistances and lengths of coils or wires. 

The ratios proved that resistance is directly proportional to the length of the material in the coils of the resistor because they were the same.

Because we previously solved for the ratios between the lengths and the resistances, we now were able to use those ratios to solve for the unknown resistance of a system that had the same length but larger diameter of coils.

Below is a derivation of a formula for CURRENT that includes both drift velocity and charge density.

The graphs below depict the current and voltage over a time lapse. They are both linear and the same. 

Summary:

• In a simple circuit, the wire must be connected from the positive end of a battery and ultimately back to the negative end in order for a continuous flow of current to occur. 
• Voltage and current have a linear relationship.
• The ratio between resistances and lengths of coils can be used to solve for more complex problems involving differing radius coil sizes.
• Resistance is equal to voltage over current.
• Voltage determines potential energy of a system.