Current electricity 9 Flashcards
What is current electricity?
Continous movement of electric charge
What is a conductor?
Substance/material that allow for free movement of charges
What is an insulator?
Substances/materials that do not allow charges
What is an electric current?
Path along which charges can move
What does a circuit need to exist?
- A closed circuit
- Source of electrical energy
Who created the light bulb?
Thomas Edison
What is the conventional current?
flow of positive charge from the positive terminal along the electric circuit back to the negative terminal
What is the series connection?
Connected end to end. single path for charges. If one component breaks, it is unable to work
What is a parallel connection?
Connected across from each other, more than one path/alternative. Continues to work
What is charge represented by?
Q
What is charge measured in?
Coulombs - C
Define current
Current is the rate of flow of electric charge. A measure of how many charges flow past a specific point over a certain time
What is the symbol for charge?
C
What is the formula for charge?
What is the potential difference?
The work done per unit of positive charge. How much work needs to be done to get a charge from one point to another (energy required)
What is the potential difference symbol?
V
What is potential difference measured in?
Volts
What is the formula for potential difference?
What is an ammeter?
A device used to measure current. Connected in series. Low resistance.
What is a voltmeter?
Measured voltage across a circuit. Connected in parallel. Volts (V). Very high resistance
Define resistance
A materials opposition to the flow of charge
What is the pattern of movement for resistance?
Movement from terminal to terminal. Zigzag path that results from countless collisions with fixed atoms within the conducting material.
Why does resistance slow down the movement of charge?
Collisions hinder the movement of the charges offering resistance
What is a resistor?
Any electrical device that experiences an energy conversion
What is the symbol of resistance?
R
What is resistance measured in?
Ohms
What is the formula of resistance?
Define Ohms Law
The current through a conductor is directly proportional to the potential difference across the conductor at a constant temperature
What is an ohmic conductor?
Obeys Ohms law. When the temperature remains constant
What is an non-ohmic conductor?
Does not obey the law. Not directly proportional
What are the factors that affect resistance?
- Length 2. Type 3. Thickness 4. Temperature
What does it mean when it is the longer the conductor?
The greater resistance
Why is there the greater resistance, the longer the conductor means?
Longer wire mean there the is more opportunities there are for the charges to collide with the conducting material.
What does the type if material relate to resistance mean?
Different materials offer different amounts of resistance to the movement of charge.
What type if wire provides lower resistance?
Thicker conductors allow charge to flow through them more freely, therefore have lower resistance than thinner wires.
What does a higher temperature result in with resistance?
A higher temperature results in the charges moving faster, and the atoms in the conductor vibrating more. The number of collisions between the charges and the conductor therefore increases, and so the resistance increases.
What is the total voltage of cells connected in series?
the total voltage is the sum of the voltages (potential differences) of individual cells.
What effect does increasing the number of cells in series have on the brightness of a bulb?
As the number of cells in series increases, the brightness in the lightbulb increases
What in a series circuit will increase the current?
Adding cells in series causes the charges in a circuit to flow at a faster rate (i.e. increases the current)
What happens when resistors are connected in series?
When resiators are connected in series, the lower the resistance in the circuit is the sum of the individual resistors.
Whal effect does increasing the number of bulbs (resistors) in series have on the brightness of the bulbs?
As the number os bulbs in series increases, the brightness of the bulbs decreases
What happens when you add resistors in series?
Adding resistors in series increases the resistance in a circuit, causing the charges in the circuit to flow at a slower rate (i.e. decreases the current).
What happens when potential difference is across the battery in series?
The total potential difference across the battery is the same as the sum of the potential differences across each of the resistors
A resistor with higher resistance will have?
High potential difference
A resistor with lower resistance will have?
A resistor with lower resistance will have a lower potential difference across it.
What happens to the current when resistors are added?
The total current decreases with each resistor added in series to the circuit i.e. resistance increases.
Is the current the same in a circuit at any given point?
Yes
What happens when you add cells in series?
Increases the size of the elecrtic current. The light bulbs will glow brighter
What happens when you add resistors in series?
Light bulb will glow more dimly. Decrease size of electric current
What is the formula for resistance in series?
Rs = R1 + R2 + R3
What happens to cells in parallel?
Total voltage is the same as the voltage of the individual cells. Cells last twice as long
What is the potential difference across each resistor in a parallel circuit?
Potential difference across each resistor is the same
What is the total current of the battery in a parallel circuit/
Total current through the battery is the same as the sum of the current through the resistor
What happens when you add resistors in parallel?
It decreases the total resistance and increases the current strength. It is split up
What is effective resistance
The resistance between two points in an electric network.
What is the formula for effective resistance?
1/rp = 1/r1 + 1/r2
must revert answer
What will the answer always be for effective resistance be?
It will always be smaller than the smallest resistor
Define Rate of electrical energy supply
. It is the amount of energy supplied per unit of time
Define power
The rate at which energy is transferred
What is the symbol for power?
P
What is power measured in?
In Watts (W)
The units for power?
W
What is the formula for electrical power?
Electrical appliances are marked with a power rating. What does this indicate?
It indicates rate of the transfer of energy.
What is the calculation of formula for electrical power transferred by an appliance?
What is energy consumpion?
It takes place over a long period time
What is the formula for energy consumption?
What is the unit of energy consumption?
Kilowatt hour (kWh)
What is 1kw =?
1000W
What is the formula for the cost of using electrical appliances?
C = U x T x P
When is the only time you should use Kilowatts and hours?
When calculating the cost of electrical consumption
