3.5.1.4 Circuits Flashcards
What is power?
Power is defined at the rate of energy transfer or the rate of work done.
What is power measured in?
Power is measured in watts (W). 1 watt is equivalent to 1 joule per second.
What is the equation for power?
Power = Energy Transfer / Time
What is the equation for the power of an electrical component?
Power = Current x Potential Difference
Describe a heating effect of a electric current.
The heating effect of an electric current in any component is due to the resistance of the component.
The charge carriers repeatedly collide with the positive ions of the conducting material.
There is a net transfer of energy from the charge carriers to the positive ions, due to collisions.
After a charge carrier loses Kinetic energy in such a collision, the force due to the p.d. across the material accelerates the charge carrier until it collides with another positive ion.
What is the power of a component with a heating effect?
Power = Current^2 x Resistance. Power = Potential Difference^2 / Resistance.
Give three equations for calculating the energy across an electrical component.
E = IVt
E =( V²/R ) x t
E = I²Rt
Give three equations for calculating the energy across an electrical component.
E = IVt
E =( V²/R ) x t
E = I²Rt
How do you convert between KWh and joules?
1 KWh = 3.6 x10^6 J
How do you convert between KWh and joules?
1 KWh = 3.6 x10^6 J
What does the conservation of charge state?
As charge flows through a circuit, it does not get used up or is not lost. Whatever charge flows into a junction in a circuit, the same amount will flow out of the junction.
What does the conservation of energy state?
Energy is conserved in a closed system.
In a closed loop circuit, the sum of the potential differences must be equal to the emf of the cell.
What does Kirchhoff’s First Law state?
The total current entering a junction is equal to the total current leaving the same junction.
What does Kirchhoff’s Second Law state?
The total electromotive force around a series circuit is equal to the sum of the potential differences across each component.
What is the rule for current in a series circuit?
The current is the same everywhere in a series circuit.
What is the rule for potential difference in a series circuit?
The potential difference is shared across components proportionally to the resistances of the components.
The emf is split between the components.
What is the rule for the total resistance for a series circuit?
The total resistance is the sum of the resistances for every resistor.
RT = R1 + R2 + R3 …
What is the rule for current in a parallel circuit?
The current splits at each junction.
What is the rule for the potential difference for a parallel circuit?
The potential difference across all branches is equal to the emf of the cell.
What is the rule for resistance in parallel circui?
The total resistance in parallel is less than the resistance of the smallest resistor.
What equation can be used when 2 resistors are given in parallel?
R total = (R1 x R2) / R1 + R2
What is the rule for the total emf of cells in series?
EMF total = EMF 1 + EMF 2 + EMF 3 ….
as long as the internal resistance of the cells is negligible.
However, this depends on the direction of the cell. If the cells are facing different directions, they must be subtracted.
What is the rule for the potential difference of identical cells in parallel?
The total emf of the combination of cells is the same size as the emf as the a single individual cell.
What is the rule for current of identical cells in parallel?
For identical cells in parallel, the current through each branch is equal to the total current divided by the number of cells there is.
