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Short Circuit - Pop Quiz
Question: What would happen if the positive and negative terminals of a
cell were connected by a wire without placing a bulb, motor, or some sort
of resistance in the circuit?
Answer: If the circuit were left on for more than a few minutes, you'd
destroy the cell and, if the current source was strong enough, you'd burn
yourself or start a fire.
Materials
- Two "D" cells in battery holders
- One flashlight bulb in lamp holder
- Two switches
- Electrical wires with 1 1/2 inches (3.75 cm) at each end stripped
bare of insulation
To Do
Assemble the circuit as shown in the diagram..
Close only switch A. What happens to the lamp? Is there a closed circuit?
If so, trace the complete circuit through which electricity flows.
Close only switch B. What happens to the lamp? Is there a closed circuit?
If so, trace the complete circuit through which electricity flows.
Bend the clip in switch A so that this switch remains on. While the lamp is
glowing, close switch B. What happens? What path does the current
follow when both switches are closed? Why? Release switch B. What
happens now? Why?
Awesome Experiments in
Electricity and Magnetism
Michael Di Spezio
Sterling Publishing, 2006
Short Circuit - Pop Quiz
The Science
Switch A controls current flow in the outer loop. When switch A is closed,
current flows along this outer path to light the lamp.
Switch B is part of a separate path that offers no resistance. When switch B
was closed, its path became complete. Since the path contained no resistors,
it acted as a short circuit. The electrons always take the path of least
resistance. The current flowed across switch B and bypassed the lamp.
Without a current flow, the lamp went out.
Check It Out! Short circuits can cause fires. When a wire offers little or no
resistance to current flow, excessive flow can heat up the conductor. If the
wire gets hot enough, it can cause burns and start fires
Awesome Experiments in
Electricity and Magnetism
Michael Di Spezio
Sterling Publishing, 2006