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Introduces the concept of invisible electric fields and the energy required to move charges within those fields.
How does a lightning bolt 'know' exactly where to strike, or how does your phone charge wirelessly without a single metal contact? The answer lies in invisible maps of energy called electric fields that fill the space around us.
An Electric Field is a region of space around a charged object where another charged object will experience a force. We visualize these fields using field lines. By convention, these lines always point in the direction a positive test charge would move. This means lines point away from positive charges and toward negative charges. The closer the lines are together, the stronger the field. Think of it like a topographical map: steep slopes (strong fields) have lines packed tightly together, while flat plains (weak fields) have lines spread far apart.
Quick Check
If you are sketching the field lines for a lone electron, which direction should the arrows point?
Answer
The arrows should point inward, toward the electron.
Calculate the electric field strength at a point away from a charge.
Quick Check
If you move three times further away from a charge, what happens to the field strength ?
Answer
It becomes of the original strength ().
How much work is required to move a charge across a potential difference of ?
Two charges, and , are placed apart. Calculate the net electric field strength exactly at the midpoint between them.
Which of the following is NOT a rule for sketching electric field lines?
If of work is done to move of charge, what is the potential difference?
The electric field strength is a scalar quantity.
Review Tomorrow
In 24 hours, try to sketch the field lines for two identical positive charges placed side-by-side and explain why they 'push' away from each other.
Practice Activity
Find a battery at home. Look at its voltage (e.g., 1.5V or 9V) and calculate how many Joules of energy it gives to every 2 Coulombs of charge that pass through it.