Summary physics ch5 circuits
5.1 Charge and voltage
Charge= A physical property of matter that
causes it to experience a force inside an
electromagnetical field.
Current (I)=The amount of electrical charge
passing a certain point per second.
Voltage (U)= A measure of the amount of
electrical energy carried by an electron.
A proton is always positive and a electron is always negative.
Neutrally charged= Equal amount of + and -.
Negatively charged= More – than +.
Positively charged= More + than -.
Electric charge can be positive (+), negative (-) or neutral.
Equal charges repel each other (+ +) (- -)
Opposite charges attract (+ -)
Charge always wants to distribute itself over the entirety of an object.
When a charged object comes into contact with a lesser charged object, the charge in both
objects will want to distribute itself across both objects. This means that electrons will start
to move. These moving electrons are what we call ‘current’.
When two points have a difference in charge, then there will be a voltage across these two
points.
Moving electrons generate electrical current.
5.2 Resistance
When two points experience a potential difference [U] (difference in level of charge), the
current [I] in between these two points is determined by the resistance [R] between these
two points.
U
Ohm’s Law= R=
I
Resistance = R = ohms = Ω
Voltage = U = volts = V
Current = I = amperes = A
l
R=ρ∙
A
ρ = Specific resistivity (Ω∙mm2/m)
l = Length (m)
A = Cross-sectional area (mm2) ( A=π r 2 )
NTC (Negative Temperature Coefficient) = Resistance drops as temperature rises.
PTC (Positive Temperature Coefficient) = Resistance increases as temperature rises.
LDR (Light Dependent Resistor) = Resistance decreases as light intensity increases.
5.1 Charge and voltage
Charge= A physical property of matter that
causes it to experience a force inside an
electromagnetical field.
Current (I)=The amount of electrical charge
passing a certain point per second.
Voltage (U)= A measure of the amount of
electrical energy carried by an electron.
A proton is always positive and a electron is always negative.
Neutrally charged= Equal amount of + and -.
Negatively charged= More – than +.
Positively charged= More + than -.
Electric charge can be positive (+), negative (-) or neutral.
Equal charges repel each other (+ +) (- -)
Opposite charges attract (+ -)
Charge always wants to distribute itself over the entirety of an object.
When a charged object comes into contact with a lesser charged object, the charge in both
objects will want to distribute itself across both objects. This means that electrons will start
to move. These moving electrons are what we call ‘current’.
When two points have a difference in charge, then there will be a voltage across these two
points.
Moving electrons generate electrical current.
5.2 Resistance
When two points experience a potential difference [U] (difference in level of charge), the
current [I] in between these two points is determined by the resistance [R] between these
two points.
U
Ohm’s Law= R=
I
Resistance = R = ohms = Ω
Voltage = U = volts = V
Current = I = amperes = A
l
R=ρ∙
A
ρ = Specific resistivity (Ω∙mm2/m)
l = Length (m)
A = Cross-sectional area (mm2) ( A=π r 2 )
NTC (Negative Temperature Coefficient) = Resistance drops as temperature rises.
PTC (Positive Temperature Coefficient) = Resistance increases as temperature rises.
LDR (Light Dependent Resistor) = Resistance decreases as light intensity increases.
