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Are you a fan of National Geographic, just like me?

If you are, I’m sure that you’ve seen many close-up pictures or videos of animals on the National Geographic channel. Have you ever wondered how a photographer can get up close to an animal as dangerous as the lion without getting hurt? How is it possible to capture photographs of the rarest and most elusive animals without startling them?

The answer is to use camera traps! In this article, I will be discussing a question on Electricity from the 2014 Red Swastika School P6 Prelim Examination Paper that will unravel the mystery of how a camera trap is able to take photos of animals without the photographer behind the camera!

Let’s take a look at the question!

Question Analysis

Source: Red Swastika School – 2014 P6 Prelim Examination Paper [Q40b]

Let’s Analyse Part (i)

“Explain clearly how this set-up enables the camera to take a photograph of the snow leopard when it steps on P.”

Before The Snow Leopard Steps on P

Firstly, let’s understand what happens before the snow leopard steps on P. When we take a look at the diagram, what do you notice? We can see that there is a gap between the iron contacts X and Y, which creates an open circuit with the camera.

Now, what happens when there is an open circuit with the camera? Electric current from the battery is unable to flow through the circuit, preventing the camera from taking a photograph.

After The Snow Leopard Steps on P

What do you think will happen when the snow leopard steps on P?

The spring will compress and become shorter, causing P to move closer to Q. This causes iron contacts X and Y to come into contact with each other.

When X and Y are touching each other, will there still be a gap in the circuit?

No, there will not be! This means that there is a closed circuit with the camera. Thus, electric current from the battery can flow through the entire circuit, including the camera. This causes the camera to take a photograph of the snow leopard.

In order to help my P5 students avoid missing out on important keywords that examiners are looking out for, I teach my P5 students the following 4-step template structure to be used when writing their answers:

Step 1: State the situation.

Step 2: Identify if there is an open/closed circuit.

Step 3: Determine if electric current can/cannot flow.

Step 4: State the outcome.

Try applying these four steps and see if you manage to get the same answer as me!

Suggested Answer for Part (i) – Primary 5

Step 1: When the snow leopard steps on P, this causes the spring to be compressed and iron contacts X and Y to touch each other.

Step 2: This forms a closed circuit (represented in blue) with the camera.

Step 3: Thus, electric current can then flow through the camera,

Step 4: allowing the camera to take a photograph of the snow leopard.

However, this answer is insufficient for P6 students as they would have learnt the topic of Forces and are expected by examiners to integrate the concepts from Forces with Electricity in order to score full marks on this question.

Let’s Further Analyse Part (i) – Primary 6

In order to answer Part (i) as a P6 student, we must first identify the force acting on the spring when the snow leopard steps on P.

What is the force that acts downwards on all objects? Yes, gravitational force! The gravitational force acting on the snow leopard exerts a downwards force on the spring, causing it to be compressed.

Suggested Answer for Part (i) – Primary 6

Step 1: When the snow leopard steps on P, the gravitational force acting on the snow leopard causes the spring to be compressed. The spring becomes shorter, causing iron contacts X and Y to touch each other.

Step 2: This forms a closed circuit with the camera.

Step 3: Electricity can then flow through the camera,

Step 4: allowing the camera to take a photograph of the snow leopard.

Let’s Analyse Part (II)

“In order to capture photos of lighter animals such as squirrels, should iron contacts X and Y be located further away from each other or closer together?”

Using the thought process from Part (i), lighter animals have a smaller mass and mass is a factor that affects gravitational force. Thus, animals with a smaller mass will have a smaller gravitational force acting on them, causing them to exert a smaller push force on the spring. Thus, the spring compresses less.

Scenario 1: X and Y Further Away From Each Other

When X and Y are further away from each other, what will happen when lighter animals step on P?

The smaller gravitational force acting on the lighter animals will cause the spring to compress less. This will cause rod P to move down less and contacts X and Y will not be able to come into contact with each other. Thus, this creates a gap in the circuit and there will still be an open circuit with the camera.

Scenario 2: X and Y Closer Together

When X and Y are closer together, what will happen when lighter animals step on P?

Even though the smaller gravitational force acting on the lighter animals will cause the spring to compress less and rod P to move down less, contacts X and Y will be able to come into contact with each other as they are closer together. This creates a closed circuit with the camera.

Based on the above 2 scenarios and analyses, would you move X and Y nearer to or further away from each other when a lighter animal is stepping on P so that a photograph of the animal can be taken?

We should bring contacts X and Y closer to each other (Scenario 2). Why? Although the spring compresses less with a lighter animal, as X and Y are now nearer to each other, they will still be able to come in contact with each other. Thus, there will still be a closed circuit with the camera, allowing electric current to flow through the camera, which allows the camera to take a photograph of lighter animals such as squirrels.

Suggested Answer for Part (II)

Iron contacts X and Y should be located closer together.

Conclusion

In this article, we have discussed how one type of camera trap works.

There are actually several different types of camera traps that are used, such as motion or infrared sensor camera traps and weight-activated camera traps. The camera trap discussed in this question is actually an example of a weight-activated camera trap.

Weight-activated camera traps usually comprise of a compressible spring between two rods, two metal contact points with wires attached to them, batteries and the camera itself.

Wildlife photographers and researchers place camera traps in places where the animal has been sighted before and they camouflage the camera trap in the environment to prevent the animal from discovering it.

When the unsuspecting animal moves about its environment and steps onto the “trigger”, the “trap” is activated and the camera takes a photograph of the animal. Camera traps are very useful to study animals living in their natural environment.

If you would like to find out more about the different types of camera traps other than the weight-activated camera trap as mentioned in this article, feel free to access this link from National Geographic: https://www.nationalgeographic.com/animals/2019/08/favorite-camera-trap-wildlife-photography/

Stay tuned for more articles coming your way! 🙂