⚡ CURRENT ELECTRICITY - FULL REVIEW
🔹 1. Electric Current
Definition: An electric charge moves through a conductor.
Charges move in general from a potential difference (or voltage).
Formula: I=Q/t
Where: I = current (in Amperes or A), Q = charge (in Coulombs or C) and t
= time (in seconds or s).
👉 1 A = 1 C/s
Direction: Current flows from a positive terminal (+) to a negative terminal
(-) and electrons flow opposite that, from a negative terminal (-) to a
positive terminal (+).
🔹 2. Electric Potential & Electric Potential Difference
Electric potential is defined as the work done to move a unit charge.
Electric potential difference is defined as the energy required to move a
charge between two points.
Formula: V=W/Q
(Units = Volts (V))
🔹 3. Ohm's Law
Ohm's Law is one of three fundamental laws that govern electricity.
According to Ohm's Law, when temperature remains constant, the current
is directly proportional to the voltage.
Formula: V=IR, Where R = resistance in Ohm (Ω).
👉 Describe the number of volts (V) using a V vs I graph.
In V vs I graph, the slope of the graph represents the resistance.
🔹 4. Resistor (Resistance)
A resistor is an object that opposes current flow.
,Formula: R=ρ L/A
(Units = Ω)
Where ρ = resistivity, A = cross-sectional area of wire and L = length of
wire.
👉 IMPORTANT: Resistor (Resistance) Facts.
Resistor resistance increases with length:
Thick wire has less resistance than does thin wire.
Resistor (Resistance) Facts Resistor characteristics include: size (length),
shape, and material.
🔹 5. Resistivity (ρ)
Resistivity (ρ) is a characteristic of a material that does not change
depending on size or shape. The resistivity of a given material is impacted
by two factors: The type of material and the temperature of the material.
Resistors of conductive materials (i.e., metals) become less resistive as
their temperature increases; therefore the resistivity of metals increases as
their temperature increases. Resistors made of semiconductive materials
will become more resistive as their temperature increases.
Resistivity is imparted by other conductive materials being connected in
series (with respect to their resistive characteristics).
🔹 6. Conductance & Conductivity
Conductance: G= 1/R
Or, G=conductance. Conductivity: σ= 1/ρ
(Units are mho's).
🔹 7. Resistor Combinations
➃ Series Connections: All series connected resistors have the
same current flowing through them. Therefore, equivalent
resistance is the sum of each of the series resistances.
Equivalent resistance formula Req=R1+R2+R3
The voltage applied to each series connected resistor will be different due
to the different resistive values of the resistors. Series combinations of
, resistors are used when their purposes is to increase total series
resistance.
➤ Parallel Connections: The voltage applied across all parallel
connected resistors is the same at each node in the parallel
connection.
1/Req=1/R1+1/R2+1/R3 Current divides
🔹 8. Electric Power
● Rate of electrical energy consumption
P=VIP = VIP=VI
Also:
P=I^2 R , P= V^2 /R
👉 Unit: Watt (W)
🔹 9. Electrical Energy
E=PtE = PtE=Pt
👉 Commercial unit:
● 1 kWh = 1 unit
🔹 10. Heating Effect of Current (Joule’s Law)
● Electrical energy converts into heat.
H= I^2RtH=I2Rt
🔹 1. Electric Current
Definition: An electric charge moves through a conductor.
Charges move in general from a potential difference (or voltage).
Formula: I=Q/t
Where: I = current (in Amperes or A), Q = charge (in Coulombs or C) and t
= time (in seconds or s).
👉 1 A = 1 C/s
Direction: Current flows from a positive terminal (+) to a negative terminal
(-) and electrons flow opposite that, from a negative terminal (-) to a
positive terminal (+).
🔹 2. Electric Potential & Electric Potential Difference
Electric potential is defined as the work done to move a unit charge.
Electric potential difference is defined as the energy required to move a
charge between two points.
Formula: V=W/Q
(Units = Volts (V))
🔹 3. Ohm's Law
Ohm's Law is one of three fundamental laws that govern electricity.
According to Ohm's Law, when temperature remains constant, the current
is directly proportional to the voltage.
Formula: V=IR, Where R = resistance in Ohm (Ω).
👉 Describe the number of volts (V) using a V vs I graph.
In V vs I graph, the slope of the graph represents the resistance.
🔹 4. Resistor (Resistance)
A resistor is an object that opposes current flow.
,Formula: R=ρ L/A
(Units = Ω)
Where ρ = resistivity, A = cross-sectional area of wire and L = length of
wire.
👉 IMPORTANT: Resistor (Resistance) Facts.
Resistor resistance increases with length:
Thick wire has less resistance than does thin wire.
Resistor (Resistance) Facts Resistor characteristics include: size (length),
shape, and material.
🔹 5. Resistivity (ρ)
Resistivity (ρ) is a characteristic of a material that does not change
depending on size or shape. The resistivity of a given material is impacted
by two factors: The type of material and the temperature of the material.
Resistors of conductive materials (i.e., metals) become less resistive as
their temperature increases; therefore the resistivity of metals increases as
their temperature increases. Resistors made of semiconductive materials
will become more resistive as their temperature increases.
Resistivity is imparted by other conductive materials being connected in
series (with respect to their resistive characteristics).
🔹 6. Conductance & Conductivity
Conductance: G= 1/R
Or, G=conductance. Conductivity: σ= 1/ρ
(Units are mho's).
🔹 7. Resistor Combinations
➃ Series Connections: All series connected resistors have the
same current flowing through them. Therefore, equivalent
resistance is the sum of each of the series resistances.
Equivalent resistance formula Req=R1+R2+R3
The voltage applied to each series connected resistor will be different due
to the different resistive values of the resistors. Series combinations of
, resistors are used when their purposes is to increase total series
resistance.
➤ Parallel Connections: The voltage applied across all parallel
connected resistors is the same at each node in the parallel
connection.
1/Req=1/R1+1/R2+1/R3 Current divides
🔹 8. Electric Power
● Rate of electrical energy consumption
P=VIP = VIP=VI
Also:
P=I^2 R , P= V^2 /R
👉 Unit: Watt (W)
🔹 9. Electrical Energy
E=PtE = PtE=Pt
👉 Commercial unit:
● 1 kWh = 1 unit
🔹 10. Heating Effect of Current (Joule’s Law)
● Electrical energy converts into heat.
H= I^2RtH=I2Rt
