Deck 2: Sensing 1

Question 1

What is ion beam machining?

Answer 1

Were argon ions are made by firing electrons at argon atoms. The ions are then accelerated into a beam and the ions knock atoms out of the material, making materials such as diamond sharper.

Question 2

Why must a beam of ions travel in a vacuum?

Answer 2

• A beam of ions carries a current

- If not the ions collide into gas molecules and scatter.

Question 3

What creates potential diffirence?

Answer 3

Uneven distributions of charge.

Question 4

Explain how a dry cell produces a potential diffirence?

Answer 4

The chemical reaction drives electrons to one pole leaving positive charge at the other. The diffirence in distribution of charges creates a potential diffirnce between poles.

Question 5

Q=
I=
V=
E=
P=
t=

Answer 5

Q= Charge in coulombs(c)
I= current in amperes(A)
V= potential diffirence in volts (V)
E=Energy in joules(J)
P= Power in watts(W)
T=time in seconds(s)

Question 6

What is electric current and what equation is used to calculate it?

Answer 6

1) Electric current is the rate of flow of charge

2) I = Q / t -> I=Current(A), Q=charge(c), T=time(s)

Question 7

What is electrical potential diffirence and what equation is used to calculate it?

Answer 7

1) Electrical potential diffirence V between two places is the diffirence in potential energy E of a charge Q going between those two places.
2) V= E / Q -> E=energy(j), Q=charge(c)

Question 8

What is power and how is it calculated?

Answer 8

Power P is the rate of electricity of energy E. P=E/t

Question 9

What is conductance?

Answer 9

Conductance is the current for a given potential diffirence.

• G=I/V
• G=1/Resistance

Question 10

What is resistance?

Answer 10

Resistance is the potential diffirence needed for a given current .

• R=V/I
• Resistance = 1/conductance

Question 11

What is the relationship between conductance and resistance?

Answer 11

They are the inverse of each other.

Question 12

What is ohms law?

Answer 12

Provided the temperature is constant, the current through an ohmic conductor is directly proportional to the potential diffirence across it.

Question 13

Give a reason to produce microchips small?

Answer 13

One reason to build microchips small is to reduce delay times.

Question 14

In parallel circuits what adds up?

Answer 14

1) Conductances add up (Gt=G1 + G2)
2) Currents add up
3) Potential diffirence remains constant

Question 15

In series circuits what adds up?

Answer 15

1) Resistances add up ( Rt=R1 + R2)
2) Current is constant
3) Potential difference adds up.

Question 16

What is the unit for conductance?

Answer 16

1) Amperes per volt

2) Siemens(S)

Question 17

What are potential dividers used for ( generally ) ?

Answer 17

Potential dividers are used to control the potential diffirence coming out of resistors.

Question 18

How do potential dividers work?

Answer 18

A potential divider taps off a fraction of its input, to provide a controlled output.

Question 19

Why do the potential dividers in fuel gauges not give a linear graph for amount of fuel left vs voltage output?

Answer 19

Many fuel gauges do not move round the dial by equal amounts for equal numbers of litres of petrol used up, the sacle is non-linear. This is because the petrol tanks have an odd shape to fit in the space available.

Question 20

What is a calibration curve?

Answer 20

A calibration curve is used to tell you how to look up the input to a measuremen system if you known its output. Calibration curves are often built into sensor systems as look up tables relating input to output..

Question 21

How can electromotive force be calculated?

Answer 21

• E= Vexternal + Vinternal

- E= IRexternal + IR internal