Electrical circuits Flashcards
What is current defined as?
the rate of flow of charge (electrons)
The current can be calculated from the expression….
Give it’s rearrangement as well.
Q = It (Charge (C) = Current (A) x Time (s)
Rearrangement:
I = Q/t
1 Amp is the same as …
1 Coulomb per second
Which way does current flow in a circuit and what is the name of this current?
Current flows from the +ve terminal to the -ve terminal
This is called ‘Convectional current’.
Which way do electrons flow in a circuit?
Front the -ve terminal to the +be terminal.
What happens to the current and resistance of a circuit with a bulb in series, when another bulb is added?
The current decreases as it is shared between the two bulbs. Therefore the resistance has increased.
Show the rules for current in a series circuit.
Current (in) = Current (out)
I1 = I2 = I Total
Name the rules for current in a parallel circuit.
A1 = A2 + A3 = ATotal
I1 = I2 + I3
What’s the formula for Resistance when it is involving potential difference and current.
R = V/I Resistance (Ohms) = P.d (V) / Current (A)
What effect does resistance have on current?
As resistance increases, current decreases which means the flow of charge is reduced.
Was does resistance affect in terms of current?
Resistance is the variable that affects the flow of charge and provides a resistive force to that flow.
What is potential difference?
Voltage or potential difference (p.d) is the energy (electrical) delivered from the power supply to the component (s), per coulomb of charge.
What is energy measured in?
Joules / J
What is charge measured in?
Coulombs / C
1 Volt =
1 J/C
In the required practical ‘Resistance of a wire’ what is resistance directly proportional to?
The length of the wire. i.e. if the length of the wire doubles the resistance doubles
What is an IV Graph?
Graph designed to show relationship between current (I) and potential difference (V) for a component.
What does the IV graph for a filament lamp show?
It shows that as current increases, p.d increases. However, they are not directly proportional. Current also increases but at a different rate.
What does gradient equal in terms of the filament lamp IV graph?
gradient = I / R or R = I / grad.
What does the IV graph for a fixed resistor show?
The graph shows a directly proportional relationship between current and p.d. It obeys Ohms law.
What does the IV graph for a diode show?
The graph shows that current flows through a diode`in only one direction, when the terminals are reversed, through a p.d is measured, there is no current.
In the IV graph for a diode how does resistance affect current?
Resistance to current is high when The resistance is increasing. But the resistance is low when the current increases.
In a series circuit what are the rules for current, potential difference and resistance?
ITotal = I1 = 12
VTotal = V1 + V2
RTotal = R1 + R2
In a parallel circuit what are the rules for current, potential difference and resistance?
ITotal = I1 + I2
VTotal = V1 = V2
1 / RTotal = 1 / R1 + 1 / R2
