Unit 1: Topic 2: Circuits Flashcards
What does p.d stand for?
Potential difference.
What does the voltage or p.d of a supply measure?
The energy given to the charges in a circuit.
What is the definition of charge?
The flow of charge around a circuit.
What is the voltage (p.d) measured in?
Volts, V.
What is the charge measured in?
Amps, A, symbol is I.
What does an ammeter measure?
Current.
What does a voltmeter measure?
P.d or voltage.
What are the short lines for in a battery?
The negative terminal.
How does a fuse melt or blow in a circuit?
When the current is too high.
Describe what a series circuit looks like.
All the components are in line with each other and are connected end-to-end.
Describe what a parallel circuit looks like.
When components are connected across each other where the current has more than one path through that part of the circuit.
How is an electric current measured?
Using an ammeter.
If an ammeter and a voltmeter are both connected to the same circuit, where should they be connected?
The ammeter should be connected in series and the voltmeter should be connected in parallel.
Describe the current in a series circuit.
It is same at all points, Ia=Ib=Ic
Describe the p.d across a series circuit.
The sum of the p.d across the components in a series circuit is equal to the voltage of the supply, Vs=V1+V2.
Describe the current in a parallel circuit.
Sum of the currents is equal to the current drawn from the supply, Ia=Ib+Ic.
Describe the p.d in a parallel circuit.
They are the same across all components, Vs=V1=V2.
What does resistance measure?
The opposition of a circuit component to the flow of charge or current through the component.
If the resistance is greater in a, how would the current through the component be described?
Smaller.
What is resistance measured in?
Ohms.
What four things does resistance depend on?
Type, length, thickness, temperature.
Resistance depends on type, what does this mean?
The better the conductor, lower the resistance.
Resistance depends of length, what does this mean?
Longer material, higher resistance.
Resistance depends of thickness, what does this mean?
Thinner material, higher resistance.
Resistance depends on temperature, what does this mean?
Higher temperature, higher resistance.
What is the potential difference measured in?
Voltage.
What is the current measured in?
Amperes.
What is the equation/relationship āR=V/Iā known as?
Ohms law.
Resistors: Resistance remains approximately ____ for different values of ____. Therefore the ratio V/I remains ____ for different current values.
Constant, current, constant.
What is the total resistance if more than one component is connected in a series circuit?
It is equivalent to one single resistor.
What is the relationship/equation of the total resistance if more than one component is connected in a series circuit?
RT = R1 + R2 + R3.
In a series circuit, is the total resistance always larger or smaller than the largest resistance value?
It is always larger.
What is the total resistance if more than one component is connected in a parallel circuit?
It is equivalent to one single resistor.
What is the relationship/equation of the total resistance if more than one component is connected in a parallel circuit?
1/Rt = 1/R1 + 1/R2 + 1/R3.
In a parallel circuit, is the total resistance always larger or smaller than the smallest resistor value?
It is always smaller.
What is a potential divider?
It is a device or circuit which uses two or more resistors or variable resistors (potentiometer) to provide a fraction of the available voltage (p.d) from the supply.
In a potential divider circuit, what is the potential difference from the supply divided across?
The resistors in direct proportion to their individual resistances.
What is the use of a Wheatstone bridge?
It is a circuit which is used for finding resistance.
What makes a Wheatstone bridge more accurate to measure resistance?
It is more accurate than a voltmeter and ammeter. It is more accurate and sensitive.
The Wheatstone bridge is more accurate than using a voltmeter and ammeter. Describe this.
The meter shows values for volts and currents with only a small error.
The Wheatstone bridge is sensitive, describe this.
Meter shows a large deflection when a small current flows through it. It has a mark which shows where the pointer is when no current flows, it does not need to have a scale.
What is the equation used when calculating the unknown resistance in a Wheatstone bridge?
R1/R2 = R3/R4.
What is the reading on a voltmeter when it is connected between 2 pairs of resistors in a Wheatstone bridge?
Zero.
If the voltmeter in a Wheatstone bridge is connected between 2 pairs of resistors, what is the Null of Deflection?
The bridge is balanced.
