Electrical Circuts Flashcards
State Kirchhoff’s first law
Kirchoff’s first law states that the sum of the currents flowing into a junction is always equal to the sum of the currents flowing out of the same junction.
State Kirchhoff’s second law
In any circut, the sum of the electromotive forces is equal to the sum of the p.d.s around a closed loop.
Explain why Kirchhoff’s second law is the conservation of energy applied to circuts.
Kirchhoff’s second law says that the total energy transferred to the charges in a circut is always equal to the total energy transfereed from charges as they move around the circut.
How is the e.m.f of a circut split between component in series?
E.m.f is split in proportion to the resistance of the component.
Use Kirchhoff’s second law to describe how e.m.f and p.d. are related in a parallel circut.
If there is more than one component on a branch, then within that branch, the sum of p.d.s across the component must equal the e.m.f in a series circut.
How is the total resistance of number of resistors connected in series determined?
The total resistance R of a nuber of resistors connected in series is equal to the sum of individual resistances.
R = R1 + R2 +….
State Kirchhoff’s first law
Kirchoff’s first law states that the sum of the currents flowing into a junction is always equal to the sum of the currents flowing out of the same junction.
State Kirchhoff’s second law
In any circut, the sum of the electromotive forces is equal to the sum of the p.d.s around a closed loop.
How is internal resistance defined?
The resistance of a source of e.m.f due to its construction, which causes a loss in energy/ voltage as the charge passes the source, sumbol r. SI unit = Ohm.
What is meant by lost volts?
Some energy is “lost” (transferrd into heat) when there is a current in the power source, and not all the energy is transferred to the charge is available for the circut. The p.d. measured at the tables of the power source (terminal p.d) is less than the actual e.m.f
What is meant by terminal p.d?
the potential difference between an electrical power source - when there is no current this is equal to the e.m.f of the source, but if there is a current in the source this is equal to the e.m.f minus the lost volts.
By using Kirchhoff’s second law, state the relationship between e.m.f, terminal p.d and lost volts.
From Kirchhoff’s second law, the relationship between e.m.f, terminal p.d and the lost volts is:
Electromotive force = terminal p.d + lost volts
Explain why the amount of “lost volts” increases hen the current in a circut is high.
In normal use the e.m.f does not change. However, changing the currents affects the lost volts and terminal p.d. Increasing the current means that more charges travel through the cell each second and so more work is done by the charges, increasing lost volts.
Which is greater: e.m.f or terminal p.d.
The e.m.f is always greater than the terminal p.d. (Unless there is no current)
Under what condition is e.m.f equal to terminal p.d?
When combining relationships.
Under the condition that you are combining the relationship.
