5.2 Heating Effects of an electric current Flashcards
Kirchhoff’s first law
The sum of the currents into a junction equals the sum of the currents away from a junction.
Kirchhoff’s second law
Energy in = Energy out
Define resistance and Ohm’s law
Resistance:
Reistance is the level of conductivity of a material. It can be defined as Potential diffrence across a componenet (V) / current across a componenet.(I)
Ohm’s law:
Ohms law says that
potential diffrence across a componenet =
Current across a componenet * Resistance of a component
Draw I/V graphs for
- ohmic conductor
- filament lamp
- semiconducting lamp
*Resistivity formula:
how does resistivity relate to lenght and cross-sectiponal area of a conductor?
Resistivity formula:
pL/A
The resistance of a given material is proportional to the length, but inversely proportional to the cross-sectional area.
What is power dissapated by resistor?
Power dissapated by a resistor or other electrical component is the waste energy (kinetic energy, …) produced.
How is dissapated power calculated?
Power dissipation formula:
P = I^2 * R
How to calculate total resistance, of resitors in series?
Resistor in a series:
R1 + R2 + R3 = RT
How to calculate total resistance, of resitors in parallel?
Formula for resistance of resistors in a series:
1/R1 + 1/R2 + 1/R3 = 1/RT
RT
How to place a voltmeter in a circuit?
In parrallel to the component u want to find the potential diffrence for.
How to place a ammeter in a circuit?
In series.
What is a variable resistor?
A resistor with changable resistance.
What is a potentiometer?
A variable resistor with a third adjustable terminal. The potential at the third terminal can be adjusted to give any fraction of the potential across the ends of the resistor.
What are the features of a primary cell?
Not recycable because of irreversible chemical reaction.
What are the features of a secondary cell?
Recycable.
What can you do with this formula:
Calculate Electrical field strenght without test charge.
