PG 544-552 - Daniel Wu

During the reading between pages 544 and 552 there contained many interesting pieces of information. The 11 pieces that I personally believe are the most important are included in this blog.

1. An electric current is simply a flow of charge. Electrons tend to flow in a conductor in a similar manner to how water flows through a pipe. However, in a conductor, there are positive and negative charges (flows negative to positive most of the time) while in a water pipe, there obviously isn't.

2. A current can be described as the rate of charge flow. There is an equation to calculate the current. Current in Amperes (I) = Charge in coulombs (Q) / Time in Seconds (t). The unit of coulombs per second was given the name of "Ampere" which then in turn is the base unit for currents.

3. It is supposedly difficult to measure the current. Luckily though, technology comes to the rescue with a tool called an ammeter which is a very conductive device used to measure current. It is made out of extremely conductive material so that no energy is lost in the process of measurement.

4. There are two types of currents; DC (Direct Current) and AC (Alternating Current). In direct currents, the current flows in a single direction from the supply (e.g. battery) to the load (e.g lightbulb). On the other hand, in alternating currents, the electrons periodically reverse the direction of flow which is provoked by the electric and magnetic forces. The path of current is known as a circuit.

5. There are many simplified illustrations for drawing circuits to speed things up. I counted 19 in the book alone, but the diagrams are confusing and could be easily misinterpreted.

6. Another example of an effective comparison is between the potential energy of electric charges and a bicycle fighting against gravitational energy on inches/declines. Work has to be done on a bike to increase gravitational potential energy. In contrast, work is also required by the power supply to increase the electrical potential energy of each coulomb of charge from a low to high value (incline). When the charge flows back through the load, the energy decreases (decline).

7. There is another equation, this time used to determine the electrical potential energy for each coulomb of charge in a circuit. It is written as V (electrical potential difference in volts) = E (energy required in joules) / Q (energy potential of a charge in coulombs). The potential difference is mostly known as voltage (the unit is called a volt).

8. One volt (V) is the electric potential(simplified explanation of #7).
difference between two points if one joule (J) is required to move one coulomb (C) of charge between two points.

9. The third equation i shall mention in this blog is the energy transferred by charge flow. The equation is written as E (energy in joules) = V (potential difference in volts) x I (current in amperes) x t (time)

10. The last main point I learned within these pages was about the instrument which is called the voltmeter. it is utilized to measure potential difference between two points. It is connected in parallel with the load to compare the potential before and following the load. It requires a large resistance that will therefore be a worse conductor than the load that it's connected to. Thus, the measurement by the voltmeter will divert only a small amount of current away from the circuit.

11. Now, the final discovery in the book is that all three equations are connected. Since V=E/Q and I=Q/t then E=VQ and Q=IT
 so therefore, in the end E=VQ=VIt.

Additional Explanation:

V=Volts (electric potential difference)
I=Amperes (current [rate of charge flow] in coulombs per second)
Q=Coulombs (original charge)
t=Time (in seconds)
E=Joules (energy)

Equation 1: I=Q/t
Equation 2: V=E/Q
Equation 3: E=VIt



This is the first blog I have ever written. I'm still quite unclear how to successfully write a proper one, so I have attempted to the best of my ability. Thank you for reading about 11 things i learned in physics today (textbook)!