Definitions Flashcards
What is the definition of power in terms of electrical forces?
It is the rate of working
What are the four factors which determine the resistivity of a conductor?
M - Material
A - Area
L - Length
T - Temperature
What unit is cable resistivity measured in?
Ω/m
Or ohms per metre
How does one calculate the total resistance across both the cable and the load?
By adding together the resistance given by the load and the cable itself.
This can be calculated by using the R = V/I.
How does one calculate the voltage drop across a load and the cable?
By adding together the total voltages used across the load and conductor and applying ohm’s law.
What is Kirchoff’s voltage law?
All voltage drops across the circuit must equal the supply voltage.
If a material is said to be ferromagnetic what does this mean?
It has a high susceptability to gaining/ being given a magnetic quality (that of repulsion or attraction to other magnetic objects).
How do you create a permanent magnet?
By aligning the magnetic domains within the material using an external magnetic field.
What is the magnetic field comprised of?
Lines of magnetic flux
True or false:
Lines of magnetic flux can cross.
False.
They cannot cross.
What determines the strength of a magnetic effect that a material exhibits?
The density of the lines of magnetic flux (Tesla).
True or false:
Whenever you pass a current through a cable, a magnetic effect is created around it (lines of flux appear around the cable).
True.
True or false:
The direction of current in a cable determines the direction of the flux.
True.
In a diagram, what is denoted by a circle with a cross through it?
The current is flowing away from the observer.
In a diagram, what is denoted by a circle with a dot in its centre?
The current is flowing towards the observer.
What direction would the lines of magnetic flux flow if:
1. The current is flowing away from the observer.
2. The current is flowing towards the observer.
- The lines of flux rotate in a clockwise fashion.
- The lines of flux rotate in an anti-clockwise fashion.
If the current of two cables are flowing away from the observer, would they attract or repel one another?
Why is this?
They would attract one another.
This is because the lines of flux are going in opposite directions, and as is the same with all magnetic effects, opposites attract.
How would one make the magnetic effect caused by current flow, in any given cable with current passing through it, stronger?
Create a coil with the cable.
True or false:
Adding an iron core to a coil of cable would reduce the amount of magnetic flux present.
False.
The amount of magnetic flux would increase.
Briefly explain the right hand grip rule
Using your right hand, make a fist with your thumb pointing at a 90 degree angle.
Your fingers follow the path of current, and your thumb will point to the magnetic north of the resultant magnetic field.
Which direction does magnetic flux flow outside of the magnet?
Outside of the magnet, the lines of flux flow from North to South.
What makes a magnet stronger?
The density of the lines of magnetic flux will make the magnet stronger (β is a measure of the number of lines of flux (φ) in 1m²)
If a current carrying conductor is placed in a magnetic field (north left, south right), and the current is flowing away from the observer, what will be:
1. The direction of motion of the conductor?
2. The direction of distortion of the magnetic field?
- The conductor will move downwards
- The magnetic field will be distorted upwards.
If a current carrying conductor is placed in a magnetic field (north left, south right), and the current is flowing towards the observer, what will be:
1. The direction of motion of the conductor?
2. The direction of distortion of the magnetic field?
- The conductor will move upwards.
- The magnetic field will be distorted downwards.
