# Laboratory Safety and Equipment

Physics I · Principles of Laboratory Practice · https://tryals.app/learn/physics-i/laboratory-safety-and-equipment

## Safety & Hierarchy

A physics laboratory requires **safety awareness** and **equipment competence**. 

The **Safety hierarchy** ranks protections from most to least effective:

| Level | Control Type | Example |
| --- | --- | --- |
| 1 | **Eliminate** | Remove the hazard |
| 2 | **Substitute** | Safer alternative |
| 3 | **Engineering** | Fume hoods, shields |
| 4 | **Administrative** | Training, procedures |
| 5 | **PPE** | Goggles, gloves |

**Tip:** Estimate expected results before starting. Wildly different numbers mean setup errors, not new physics.

**Common pitfall:** Meter placement. An **ammeter** in parallel acts as a short circuit. A **voltmeter** in series blocks current. Know internal resistances to avoid blowing fuses.

## Instruments & Notebooks

Precision depends on correct **instrument reading** rules:

| Instrument | Measures | Resolution |
| --- | --- | --- |
| **Vernier caliper** | Length | $\pm 0.02$ mm |
| **Micrometer** | Thickness | $\pm 0.01$ mm |
| **Digital balance** | Mass | $\pm 0.01$ g |
| **Multimeter** | $V$, $I$, $R$ | Varies |
| **Oscilloscope** | Signals | $\mu$s |

**Reading rules:**
- **Analogue:** Read to half the smallest division.
- **Digital:** The last displayed digit is the resolution.
- **Vernier scales:** The aligned mark gives the extra digit.

**Lab notebook rules:** Record **all** data directly in pen, never loose paper. Cross out mistakes—do not erase. Always include dates, setup sketches, and units.

## Practice questions

6 of this lesson's 13 practice questions, with answers. The full set is in the app.

### 1. A multimeter set to measure **current** has near-zero internal resistance. What happens if you connect it directly **across** a battery’s terminals (as if measuring voltage)?

A. It reads zero because no circuit is attached
B. A dangerous short circuit through the meter
C. It safely reads the battery’s current rating
D. Nothing; meters are input-agnostic

**Answer:** B. A dangerous short circuit through the meter

**Why:** An ammeter is deliberately a near-perfect conductor so it won’t disturb the current it measures, placed across a source, it **becomes** the circuit, and $I = V/R$ with tiny $R$ means a blown fuse at best. Knowing *why* the rule exists is what makes it stick.

Page: https://tryals.app/practice/physics-i/laboratory-safety-and-equipment/a-multimeter-set-to-measure-current-has-near-zero-internal

### 2. Match each measuring instrument to what it reads and how it connects.

**Answer:**

- Voltmeter → Potential difference, in parallel, high internal resistance
- Ammeter → Current, in series, near-zero internal resistance
- Micrometer screw gauge → Lengths to 0.01 mm
- Oscilloscope → Voltage as a function of time

**Why:** The design rule is "measure without disturbing": voltmeters siphon negligible current (high R, parallel), ammeters drop negligible voltage (low R, series). The instrument’s connection is not convention, it is physics.

Page: https://tryals.app/practice/physics-i/laboratory-safety-and-equipment/match-each-measuring-instrument-to-what-it-reads-and-how-it-connects

### 3. When diluting a concentrated acid, you should add water to the acid.

**Answer:** False

**Why:** False. Always add **acid to water**. Dilution is strongly exothermic, and pouring water onto concentrated acid heats a small volume fast enough to boil and spit corrosive liquid out of the vessel. Adding acid to a larger volume of water spreads the same heat through enough thermal mass to absorb it.

Page: https://tryals.app/practice/physics-i/laboratory-safety-and-equipment/when-diluting-a-concentrated-acid-you-should-add-water-to-the-acid

### 4. Safety procedures specify what to do BEFORE an experiment as well as during it. Why is the preparation stage weighted so heavily?

A. Because preparation is easier to inspect and enforce than behaviour
B. Because most accidents happen before the experiment starts
C. Because the equipment is more dangerous when idle
D. Because most accidents remove the chance to react

**Answer:** D. Because most accidents remove the chance to react

**Why:** Controls have to be in place before the hazard is live. Knowing where the eyewash is has to happen while you can still see.

Page: https://tryals.app/practice/physics-i/laboratory-safety-and-equipment/safety-procedures-specify-what-to-do-before-an-experiment-as-well-as

### 5. Which are correct safety procedures in a physics laboratory?

A. It is acceptable to eat and drink at the lab bench if careful
B. Wear safety goggles when working with projectiles or lasers
C. Know the location of the fire extinguisher and first aid kit
D. Never work alone with high-voltage equipment

**Answer:** B. Wear safety goggles when working with projectiles or lasers; C. Know the location of the fire extinguisher and first aid kit; D. Never work alone with high-voltage equipment

**Why:** No food/drink in labs; goggles, buddy system for hazards, and emergency equipment knowledge are required.

Page: https://tryals.app/practice/physics-i/laboratory-safety-and-equipment/which-are-correct-safety-procedures-in-a-physics-laboratory

### 6. Order the correct response to a chemical spill on skin.

**Answer:**

1. Alert people nearby and call for help if needed
2. Remove contaminated clothing
3. Flush the affected area with water for at least 15 minutes
4. Consult the safety data sheet (SDS) for specific treatment
5. Seek medical attention if irritation persists

**Why:** Immediate flushing is critical; always check the SDS and seek medical help if needed.

Page: https://tryals.app/practice/physics-i/laboratory-safety-and-equipment/order-the-correct-response-to-a-chemical-spill-on-skin