AMPP Cathodic Protection Technologist (CP3) Practice Questions — 10 Free (2026)
Answer them, then check the reasoning and the clause each one comes from. No account, no card, nothing to dismiss.
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An anode has a driving voltage of 0.75 V against the polarised structure and a circuit resistance of 15 ohms. What is its output?
Worked answers
All ten AMPP Cathodic Protection Technologist (CP3) questions with the correct option, why it is correct and the paragraph it comes from. Attempt them above first — the reasoning is worth more than the key.
Show the ten answers and their references
- Q1 · AMPP CP3 · Closed book
An anode has a driving voltage of 0.75 V against the polarised structure and a circuit resistance of 15 ohms. What is its output?
- A. 5 mA
- B. 20 mA
- C. 50 mA ✓
- D. 112 mA
- E. 200 mA
Dividing 0.75 volts by 15 ohms gives 0.05 amperes, or 50 milliamperes, a typical single anode output. Multiplying the values or misplacing a decimal produces the other answers. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 8.1
- Q2 · AMPP CP3 · Closed book
Why is internal cathodic protection limited to particular applications?
- A. Because current spreads poorly inside a small bore, so it suits tanks and vessels rather than long pipelines ✓
- B. Because internal surfaces cannot be protected by any electrochemical means at all in every case without exception
- C. Because internal protection requires a criterion that no standard recognises
- D. Because internal protection would raise the operating pressure beyond its limit
- E. Because internal protection prevents the product from flowing through the line
Throwing power inside a pipe is very limited, so internal protection is used in tanks, heat exchanger water boxes and similar geometries rather than along pipelines. An impossibility, missing criteria, pressure and flow obstruction are all incorrect. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 6.3
- Q3 · AMPP CP3 · Closed book
Why is the on potential alone insufficient on a line running through rock or dry sand?
- A. Because such ground sets the wall thickness of the pipeline
- B. Because such ground sets the coating colour of the pipeline
- C. Because the high resistivity produces a large soil voltage drop ✓
- D. Because such ground sets the internal pressure of the pipeline
- E. Because such ground sets the calibration of the survey instrument
The more resistive the path, the larger the drop included in an uninterrupted reading. Wall thickness, colour, pressure and calibration are unrelated. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 3.1
- Q4 · AMPP CP3 · Closed book
Why does electrode placement distance matter to data validity?
- A. Because placement distance has no effect, potential being a property of the structure alone
- B. Because a more distant electrode always gives a less negative reading than a close one
- C. Because placement distance affects readings only when the current is switched off
- D. Because the further the electrode, the more soil voltage drop is captured ✓
- E. Because placement distance affects current measurements rather than potential ones
Current passing through the soil resistance between the two points adds an error that grows with separation, which is why close placement over the line is the rule. No effect, a uniformly less negative result, an off-only effect and a current-only effect are all wrong. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 3.6
- Q5 · AMPP CP3 · Closed book
Why is aluminium attacked at potentials that protect steel adequately?
- A. Because aluminium is more noble than steel and so requires less protection in every case without exception
- B. Because aluminium cannot be cathodically protected in any circumstances
- C. Because aluminium conducts current more readily than steel does in soil
- D. Because it is amphoteric ✓
- E. Because aluminium always corrodes faster than steel in every environment
Amphoteric metals dissolve in strongly alkaline conditions, which is exactly what cathodic reactions produce at the surface. Nobility, an inability to protect it, conductivity and universally faster corrosion are all incorrect. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 7.3
- Q6 · AMPP CP3 · Closed book
A four pin survey uses 3.0 m spacing and the instrument reads 2.4 ohms. What is the resistivity in ohm metres?
- A. 0.80 ohm m
- B. 7.20 ohm m
- C. 45.24 ohm m ✓
- D. 90.48 ohm m
- E. 452.40 ohm m
In the equally spaced arrangement the resistivity is two pi times the spacing times the measured resistance. Omitting the factor, or using only the spacing, gives the incorrect values. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 1.1
- Q7 · AMPP CP3 · Closed book
Why does a well-coated pipeline develop a higher induced voltage than a poorly coated one?
- A. Because the coating gives a high resistance to earth ✓
- B. Because the coating conducts the induced current along the pipeline more readily than bare steel
- C. Because coated pipelines are always installed closer to power lines than bare ones
- D. Because the coating increases the magnetic coupling with the overhead conductors
- E. Because the coating reverses the polarity of the induced voltage on the structure
A sound coating isolates the steel from earth, so the voltage induced along the run has nowhere to discharge and accumulates. Conduction along the coating, installation practice, increased coupling and polarity reversal are all incorrect. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 5.1
- Q8 · AMPP CP3 · Closed book
A bare tank bottom of 450 square metres requires 20 mA per square metre. What total current is needed?
- A. 4.5 A
- B. 9.0 A ✓
- C. 18.0 A
- D. 45.0 A
- E. 90.0 A
Multiplying 450 square metres by 20 milliamperes per square metre gives 9000 milliamperes, or 9.0 amperes. Halving, doubling or misplacing the conversion produces the other answers. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 9.1
- Q9 · AMPP CP3 · Closed book
Why is the affected structure inspected internally or by inline tools after severe interference?
- A. Because inspection sets the coating colour of the affected line
- B. Because metal may already have been lost ✓
- C. Because inspection sets the internal pressure of the affected line
- D. Because inspection sets the resistivity of the soil at the discharge
- E. Because inspection sets the calibration of the survey instruments
Stopping the interference does not restore the metal that has already gone. Colour, pressure, resistivity and calibration are not the reason. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 4.2
- Q10 · AMPP CP3 · Closed book
Why are potentials monitored at several points during a current requirement test?
- A. Because the current must satisfy the criterion at the remote points as well as near the temporary drain point ✓
- B. Because the potential at the drain point cannot be measured while current is being applied in every case without exception
- C. Because monitoring several points establishes the calibration status of the instruments
- D. Because the criterion applies only at the point where the current is being applied
- E. Because monitoring several points determines the reference electrode type to use
Attenuation means the far ends of a section are the controlling locations, so the demand is set by what they need. Measurement difficulty at the drain point, calibration, a single-point criterion and electrode selection are all incorrect. AMPP CP 3 Cathodic Protection Technologist course manual and exam preparation guide, 3.3
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