Transmitting electricity

Question 1

electric current

Answer 1

Current (electric is) the rate of flow of electric charge

Question 2

Voltage/potential difference

Answer 2

Voltage is a measure of the change in the stored electrical energy per unit charge associated with the difference between two positions in an electric field.

Question 3

Resistance (electrical)

Answer 3

Resistance is a measure of the opposition to the flow of electric current

Question 4

Resistor

Answer 4

A resistor is an electrical component that resists the flow of electric current and causes a drop in voltage. Components such as light bulbs and heaters can be modeled as resistors

Question 5

Series circuit

Answer 5

Series circuit is an electric circuit where components are connected one after the other so that there is only one path along which charge can flow

Question 6

RMS (root mean square)

Answer 6

RMS (root-mean-square) is a measure of a time-varying (such as AC) voltage or current. A constant DC voltage or current with the same value as the RMS would deliver the same average power

Question 7

Transformer

Answer 7

Transformer a device that uses electromagnetic induction to transfer power from one electrical circuit to another, commonly with an exchange of current for voltage, or vice versa, while (ideally) keeping the power constant

Question 8

Load (electrical)

Answer 8

Load (electrical) is a part of an electrical circuit which consumes power.

Question 9

Define Ohms Law and Formula

Answer 9

Ohm’s law defines the relationship between the voltage across an electrical component, the current through the component, and the resistance of the component. This given through the formula V=RI V = voltage between two points in a circuit (V) R = resistance between the two points (Ω), I = current flow between the two points (A)

Question 10

Diagrams of circuit components and its circuit symbol.

Answer 10

Question 11

Resistors in a series and its formula

Answer 11

The total resistance of the number o resistors connected in series is the sum of their individual resistances.

R_T = R₁ + R₂ + …+ R_n

R = resistance (Ω)

Question 12

Power in electric circuits formulas

Answer 12

P=VI**

P=I²R=V²/R

P = power (W), I = current (A), R = resistance (Ω), V = voltage (V)

*The equation was derived through understanding that V=ΔE/ΔQ and I=ΔQ/ΔT

Question 13

What is the RMS Theory of an AC supply?

Answer 13

As an AC (alternating current) has a changing direction of current, voltage, and power this results in a sinusoidal graph. There are three alternatives descriptions which are the RMS, Peak to Peak, and Peak to both voltage and current.

The peak value describes the amplitude (maximum value) of the voltage or current.

The peak-to-peak value describes the difference between the maximum and the minimum values.

The RMS value is a fixed proportion of the peaked value which is the square root of the voltage squared.

Question 14

Diagram of a labeled RMS, Peak, Peak to Peak AC Graph

Answer 14

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Question 15

Formulas for finding V_RMS and I_RMS

Answer 15

Question 16

What is the comparison between the RMS and a DC supply? Provide the formula/s relevant

Answer 16

Question 17

What does a transformer consist of and how does it operate?

Answer 17

A transformer consists of two coils of wire (primary and secondary) wrapped around the same iron core.

The Transformer can operate once an AC current flows through the coils which produces a change in magnetic fields. This field is produced via the primary coil and then guided through the iron core to the secondary coil to create a changing magnetic flux.

Question 18

As a transformer with an AC current which causes a changing magentic flux what is induced?

Answer 18

According to Faradays law a change in magnetic flux will result in an EMF and a current in the secondry coil.

Question 19

What occurs when a transformer is induced with a DC current

Answer 19

The magnetic flux in the secondary coil would also be constant, which means that no EMF would be induced in the secondary coil.

Question 20

What is an ideal transformer and what does that result with?

Answer 20

An Ideal transformer means that all of the power delivered to the primary coil is transferred to the secondary coil. Which gives the formula:

P₁ = P₂ so V₁ I ₁ = V₂ I ₂

Question 21

What is the relationship with the primary and secondry coil within a transformer?

Answer 21

Question 22

Step-up transformer

Answer 22

A step-up transformer is one where the voltage in the secondary side is greater than the voltage in the primary side.

Question 23

Step Down transformer

Answer 23

A step-down transformer is one where the voltage in the secondary side is less than the voltage in the primary side.

Question 24

What are the properties of a step-up transformer?

Answer 24

The number of turns in the secondary coil is greater than the primary coil. (N₁<n>2) </n>

The voltage in the secondary coil is higher than the primary voltage V₁ < V₂

The current decreases from the primary coil to the secondary coil making I₁>I₂

Question 25

What are the properties of a step-down transformer?

Answer 25

The number of turns in the secondary coil is less than the primary coil. (N1\>N2) The voltage in the secondary coil is lower than the primary voltage V1 \>V2 The current increases from the primary coil to the secondary coil making I1

Question 26

What does simple power transmission system consist of?

Answer 26

A power system consist of a power supply/ generator, transmission lines, and a load (an electrical circuit that consumes power)

Question 27

What is the formula regarding voltage drops that follows Ohms law?

Answer 27

V_drop = I_line R_line V_drop = voltage drop across the transmission lines (V) I_line = current in the transmission lines (A) R_line = resistance of the transmission lines (Ω)

Question 28

What is the formula/s to power loss due to the resistance in the transmission lines?

Answer 28

P_loss = V_drop I_line = I_Line²R_line P_loss = power loss in the transmission lines (W) V_drop = voltage drop across the transmission lines (V), I _line = current in the transmission lines (A) R_line = resistance of the transmission lines (Ω)

Question 29

What is the formula for the power delivered to the load?

Answer 29

The power delivered to the load will be the difference between the power supply and the power loss. P_load = P_sup − P_loss \*This also applys to Transformers

Question 30

What is one advantage of AC power to DC power?

Answer 30

AC power has an advantage over DC power for the transmission of electricity because transformers can be used.

Question 31

Why does a transformer and DC power not work?

Answer 31

A Transformer cannot work on DC because, the primary coil will create a uniform and constant magnetic field, which will fail to induce EMF in the secondary coil.

Question 32

Advantagesof AC power

Answer 32

The advantage of AC power as a domestic power supply is its compatibility with transformers which can reduce power loss. This is due to that transformers require changing current that only benefits from AC power.

Question 33

How are transformers used to reduce power loss?

Answer 33

As electrical power is the product of current and voltage (P = VI) this means different levels of voltage and current can create the same amount of Power. As it is found both voltage drop and power loss is related to current by therefore reducing current it can allow for minimal power loss. Therefore using a low current but high voltage results in less power loss which is shown through the formula: (P_loss = I_line² R_line ) Voltage drop is also dependant on current as shown through: V_drop = I_lineR_line

Question 34

How can a step-up transformer affect the power supply to the transmission lines?

Answer 34

A step-up transformer between the power supply and the transmission lines allows power to be generated at a high current/low voltage and be transmitted at a low current/ high voltage.

Question 35

How can a step-up transformer affect the power to the transmission lines and the load?

Answer 35

A step-down transformer between the transmission lines and the load allows power to be transmitted at a low current/high voltage and be consumed at a high current/low voltage