| EQUATION | VARIABLES | WHEN TO USE |
| F=Kqq/d2 | F is the force acting between charges
K = 9x109 q is the charge of each d is the distance between the charges |
When dealing with point charges |
| F=qE | E is the magnitude of the electric field | With a point charge in a uniform E-field |
| E=Kq/d2 | To find the E-field caused by a point charge | |
| DW=qDV | W= work done to move a point charge
V= voltage(potential difference) |
When moving a point charge to a different potential |
| V=Ed | V= potential difference between two points | In a uniform E-field |
| V=Kq/d | V= potential difference between a point charge and a point | In an E-field caused by a point charge |
| q=CV | C= capacitance | |
| C=KeoA/d | K= Dialectric constant (depends on medium),
ratio to permittivity of a vacuum
eo=permittivity of a vacuum= 8.85x10-12 C2/Nm2 A= the area of the parallel plates d= distance between the parallel plates |
With a parallel plate capacitor |
| W=E=qV/2=CV2/2 | E= energy stored in a capacitor
W= work done by a capacitor when its energy is released |
With a parallel plate capacitor in a circuit |
| q=It | I= current
t= time |
With charge moved through a wire over time |
| V=IR | R= resistance | A current moving through a wire |
| R=rL/A | r= resistivity
of a certain metal
L= the length of the wire A= the cross-sectional area of the wire |
To find the resistance of a wire |
| P=IV=I2R=V2/R | P= power | To find the power supplied by a resistor |
| Rts=R1+R2+...+Rn | Rts= total resistance in a
series circuit
n=number of resistors |
series circuit |
| 1/Rtp=1/R1+1/R2+...+1/Rn | Rtp= total resistance in a parallel circuit | parallel circuit |