static electricity Flashcards
Like charges _____.
Unlike charges ______.
Like charges repel, unlike charges attract
What is the formula for electric charge?
Q = It, where
Q: charge (SI unit: Coulomb, C)
I : electric current (SI unit: Ampere, A)
t : time (SI unit: second, s)
How to charge insulators?
Charging by friction, where two insulators are rubbed against each other. The outer electrons of one material are scraped off and transferred to the other.
If two materials are rubbed together, the one higher/lower on the _______ ______ should give up electrons and become positively charged.
If two materials are rubbed together, the one higher on the triboelectric series should give up electrons and become positively charged.
How to charge 2 conductors?
Induction. Place the 2 conductors in contact on insulating stands, bring a negatively charged rod near the two conductors. The negative charges in the rod repel the electrons in the nearer sphere and they move further away. Since both spheres are touching, some electrons in nearer sphere will be repelled to the further end of other sphere.
- Nearer sphere loses some electrons and becomes positively charged.
- Further sphere gains some electrons and becomes negatively charged.
With the negatively-charged rod still in place, separate the two conductors. THEN remove the rod. The charges re-distribute themselves immediately.
How to charge 1 conductor?
Place a negatively charged rod near the uncharged single conductor (e.g. metallic sphere). The negative charges repel the conductor’s electrons to its further end. Touch the conductor for a short while. (human body is regarded as a good conductor of electricity hence excess charges in the conductor will flow through the body down to earth). Keeping the negatively charged rod stationary, remove the finger from the conductor. THEN remove the negatively charged rod. The positive charges remaining in the single conductor will re-distribute themselves uniformly.
What is discharging?
Discharging is the process in which a charged body is removed of excess charges from it. When a charged body is discharged, it is said to be neutralised.
How to discharge an insulator and conductor?
Insulator: pass over flame
Conductor: earth it (aka touch it)
What is an electric field?
An electric field is a region where an electric force is exerted on any electric charge placed within the influence of the electric field. It is represented by (imaginary) field lines.
The electric field direction is drawn from a ______ charge to a ______ charge.
The electric field direction is drawn from a positive charge to a negative charge.
