Nov. 4 – Current

First I checked your homework from last week.  Here are the solutions to the first two questions.

• Power and Efficiency Problems - Solutions 

When I checked homework, many people did not do them.  I will not post full solutions until everyone has given them a try on their own.

Review of Circuits

We did a quick review of circuit diagrams:

I pointed out that not all circuits are strictly series or parallel.  The above example shows bulbs that are in series as well as parallel.

• Bulb A and C are in series.
• Bulb B and C are in series.
• Bulb A and B are in parallel.

Then we moved on to chapter 13.3

Current

Current is the amount of charge flowing per second.

Current is measured in units of Amperes (A).

How much is 1 A?

    1 A  is the same as 6.2e18 electrons per second!

The following table shows how your body would react to different amounts of current:

It turns out 1 A is a lot of current and will likely kill you if it goes through your body!

Based on the table, how much current is in a taser?

A taser delivers an electric shock that will cause a person to lose control of their body and collapse.
This will be in the 30 mA range.

Too much current can also damage electronic devices.  There are ways to control the amount of current in a circuit:

• A fuse is a wire that will break if the current gets too high.
• Resistors can be used to reduce current.

Current is measured using an ammeter.  The symbol for an ammeter is:

Ammeters must be connected in series.

Homework

• Practice more circuit diagrams. P 554 # 1-6