| How to know the sign of the IR=dif.V in a resistor? | If the direction of I(current) is the same in which you are transversing, the IR should be negative=drop in the IR.
If the direction of I(current) is the opposite in which you are transversing, the IR should be positive= rise in the IR. |
| How to know the sign of the epsylon=dif.V in a source of Electro Motif Force(battery)? | If the direction of the EMF is the same in which you are transversing (from - to +), the dif.V should be a positive= rise in the IR.
If the direction of the EMF is the opposite in which you are transversing (from + to -), the dif.V should be negative= drop in the IR. |
| Current: | Time rate flow of charge through a surface. |
| SI Current unit | Ampere=C/s |
| With what formula is the current related to the motion of the charge carriers? | I=nqvA
n=#of mobile charge carriers per vol.
v=drift speed.
A= cross area of the conductor |
| Reistance? | Ohms law
Dif.V=RI |
| SI of resistance | ohms=V/A |
| Formula for resistivity of a conductor with a length l and a cross-area A: | R=p(l/A)
p= electrical resistivity |
| What does p=p0(1+a(T-T0)) state? | That resistivity varies according temperature. |
| What does R=R0(1+a(T-T0)) state? | That resistance varies according temperature. |
| Power? | The amount of power delivered to a device. |
| How can you calc. the Power delivered to a resistor? | P=I^2R=dif.V^2/R |
| Kilowatt-hour: | Amount of energy converted in one hr by a device supplied w/power at a rate of 1kW. |
| Sources of emf? | Battery or generator, increases the electric potential energy of charges in an electric circuit. |
| Dif. between batteries and generators? | Batteries convert chemical energy into electrical potential energy, and generators convert mechanical energy into electrical potential energy. |
| How the terminal voltage dif.V of a battery is calc? | Dif.V=E-Ir
E=emf of the battery
r=internal resistance of the battery (small) |
| Resistors in series: | - Req=R1+R2+...+Rn
- Dif.V=Dif.V1+Dif.V2= IR1+IR2=IReq |
| Resistors in parallel: | - Req=1/(1/R1)+(1/R2)
- I= I1+I2=(dif.V/R1)+(dif.V/R2)= dif.V/Req |
| What have a Simple RC circuit? | A battery, a resistor, and a capacitor in series. Or a resistor and a capacitor. |
| How a charge on the capacitor on a RC cicuit is calculated ? | q=Q(1-e^(-t/RC)) or q=Qe^(-t/RC) when the RC circuit has only a resistor and a capacitor. |
| When does the Kirchhoff's Rules (Radiation) are used? | When the resistors are connected and the circuits formed cannot be reduced to a single eq resistor. |
| Explain the 2 Kirchhoff's Rules | - Junction Rule(conservation of charge): The sum of the currents entering a juction= sum of the currents leaving that junction. I1=I2+I3
-Loop rule (conservation of energy): The sum of the V dif of all the elements around any closed circuit loop=0. |
| How to apply Kirchhoff's Rules: | - Assign symbols & directions to the currents I: If the direction of a current is incorrect, the ans=- but the correct magnitude.
- Use junction rule.
- Choose CCW or CW direction to transverse the loops: Record V rises & drops.
- Loop rule.
- Solve a single variable. |
