Virtual Electricity Lab: Lesson 4- Fuses and Schematic Diagrams

by Alan Zisman (c) 2003

If too much electrical current passes through a wire, the wires heat up and can start a fire. Too prevent this, electrical circuits in your house and in most appliances use fuses. A fuse is a type of resistor that burns up and breaks if too much electricity goes through it. When the fuse blows out, it breaks the electrical circuit, so the electricity stops flowing... that way, there’s no fire. Of course, you need to replace the fuse to make the circuit work again-- and fix whatever caused the problem in the first place.

(Houses now use a kind of fuse called a circuit breaker-- which works like a switch. Instead of burning out, the circuit breaker turns the switch off. You just need to turn it back on to make the circuit work again).

Open Virtual Electricity Lab. Make a simple circuit using the following:

Make a circuit that looks something like this:

Flip the switch on.


1. What happened? ____________________



2. If the fuse blew (and the bell stopped ringing), try each different fuse... find the lowest power fuse that will let the bell ring without blowing out.

That fuse was rated at _____ amps.


3. Add a second 9 volt battery to your circuit. What size fuse do you have to use to handle the additional electrical power without blowing out?

_____ amps


4. Click on the button labelled View Schematic. A schematic diagram uses symbols to represent the parts in an electric circuit.

Copy the schematic diagram of the circuit that you just made:



5. Draw the schematic diagram symbol for a battery: _____________

6. Draw the schematic diagram symbol for a switch: ______________

Review questions:

Define the following electricity terms:

1. electron: ________________________________________________

2. Circuit: ________________________________________________

3. Load: __________________________________________________

4. Conductor: ______________________________________________

5. Insulator: _______________________________________________

6. Resistors: _______________________________________________

7. Fuse: __________________________________________________

8. Circuit breaker: __________________________________________

9. Label the following circuits as either series or parallel: