Unit 1: Topic 2: Circuits

Question 1

What does p.d stand for?

Answer 1

Potential difference.

Question 2

What does the voltage or p.d of a supply measure?

Answer 2

The energy given to the charges in a circuit.

Question 3

What is the definition of charge?

Answer 3

The flow of charge around a circuit.

Question 4

What is the voltage (p.d) measured in?

Answer 4

Volts, V.

Question 5

What is the charge measured in?

Answer 5

Amps, A, symbol is I.

Question 6

What does an ammeter measure?

Answer 6

Current.

Question 7

What does a voltmeter measure?

Answer 7

P.d or voltage.

Question 8

What are the short lines for in a battery?

Answer 8

The negative terminal.

Question 9

How does a fuse melt or blow in a circuit?

Answer 9

When the current is too high.

Question 10

Describe what a series circuit looks like.

Answer 10

All the components are in line with each other and are connected end-to-end.

Question 11

Describe what a parallel circuit looks like.

Answer 11

When components are connected across each other where the current has more than one path through that part of the circuit.

Question 12

How is an electric current measured?

Answer 12

Using an ammeter.

Question 13

If an ammeter and a voltmeter are both connected to the same circuit, where should they be connected?

Answer 13

The ammeter should be connected in series and the voltmeter should be connected in parallel.

Question 14

Describe the current in a series circuit.

Answer 14

It is same at all points, Ia=Ib=Ic

Question 15

Describe the p.d across a series circuit.

Answer 15

The sum of the p.d across the components in a series circuit is equal to the voltage of the supply, Vs=V1+V2.

Question 16

Describe the current in a parallel circuit.

Answer 16

Sum of the currents is equal to the current drawn from the supply, Ia=Ib+Ic.

Question 17

Describe the p.d in a parallel circuit.

Answer 17

They are the same across all components, Vs=V1=V2.

Question 18

What does resistance measure?

Answer 18

The opposition of a circuit component to the flow of charge or current through the component.

Question 19

If the resistance is greater in a, how would the current through the component be described?

Answer 19

Smaller.

Question 20

What is resistance measured in?

Answer 20

Ohms.

Question 21

What four things does resistance depend on?

Answer 21

Type, length, thickness, temperature.

Question 22

Resistance depends on type, what does this mean?

Answer 22

The better the conductor, lower the resistance.

Question 23

Resistance depends of length, what does this mean?

Answer 23

Longer material, higher resistance.

Question 24

Resistance depends of thickness, what does this mean?

Answer 24

Thinner material, higher resistance.

Question 25

Resistance depends on temperature, what does this mean?

Answer 25

Higher temperature, higher resistance.

Question 26

What is the potential difference measured in?

Answer 26

Voltage.

Question 27

What is the current measured in?

Answer 27

Amperes.

Question 28

What is the equation/relationship ‘R=V/I’ known as?

Answer 28

Ohms law.

Question 29

Resistors: Resistance remains approximately ____ for different values of ____. Therefore the ratio V/I remains ____ for different current values.

Answer 29

Constant, current, constant.

Question 30

What is the total resistance if more than one component is connected in a series circuit?

Answer 30

It is equivalent to one single resistor.

Question 31

What is the relationship/equation of the total resistance if more than one component is connected in a series circuit?

Answer 31

RT = R1 + R2 + R3.

Question 32

In a series circuit, is the total resistance always larger or smaller than the largest resistance value?

Answer 32

It is always larger.

Question 33

What is the total resistance if more than one component is connected in a parallel circuit?

Answer 33

It is equivalent to one single resistor.

Question 34

What is the relationship/equation of the total resistance if more than one component is connected in a parallel circuit?

Answer 34

1/Rt = 1/R1 + 1/R2 + 1/R3.

Question 35

In a parallel circuit, is the total resistance always larger or smaller than the smallest resistor value?

Answer 35

It is always smaller.

Question 36

What is a potential divider?

Answer 36

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.

Question 37

In a potential divider circuit, what is the potential difference from the supply divided across?

Answer 37

The resistors in direct proportion to their individual resistances.

Question 38

What is the use of a Wheatstone bridge?

Answer 38

It is a circuit which is used for finding resistance.

Question 39

What makes a Wheatstone bridge more accurate to measure resistance?

Answer 39

It is more accurate than a voltmeter and ammeter. It is more accurate and sensitive.

Question 40

The Wheatstone bridge is more accurate than using a voltmeter and ammeter. Describe this.

Answer 40

The meter shows values for volts and currents with only a small error.

Question 41

The Wheatstone bridge is sensitive, describe this.

Answer 41

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.

Question 42

What is the equation used when calculating the unknown resistance in a Wheatstone bridge?

Answer 42

R1/R2 = R3/R4.

Question 43

What is the reading on a voltmeter when it is connected between 2 pairs of resistors in a Wheatstone bridge?

Answer 43

Zero.

Question 44

If the voltmeter in a Wheatstone bridge is connected between 2 pairs of resistors, what is the Null of Deflection?

Answer 44

The bridge is balanced.