[Part 3]- Required practicals🥼 🔭

Question 1

Describe how to investigate the factors, affecting the resistance of electrical currents. 📏 [6]

Hint: set up, role, attach, bewteen crocodile clips, further, changed

Answer 1

1) set up a: ammeter, battery, voltmeter and the length of wire.

2) the ammeter measures the current in the circuit; the voltmeter measures the potential difference across the wire.

3) attach a wire to a metre ruler using tape, and connect the wire to the rest of the circuit, using two crocodile clips.

4) only the wire between the crocodile clips, is connected to the circuit.

5) move the crocodile clips further apart, to increase the length of the wire, in the circuit.

6) the length of wire can then be changed, to measure the resistance of the circuit

Question 2

What can you tell me about the graph of the results, with the resistance against length of wire ? 📏

Hint: proportional

Answer 2

• a straight line will pass through zero.
• meaning, the resistance of the wire is directly proportional to the length.

Question 3

What is the problem of this required practical ? 📏

Hint: small resistance

Answer 3

• there is a small resistance, when the length of the wire is zero- this is zero error.

Question 4

What is zero error ? 📏

Hint: reading

Answer 4

• zero error, is a reading on a measuring instrument when the value should be error.
• it’s a systematic error, and can’t be reduced by carrying out repeats.

Question 5

What should you do, if zero error occurs [in the case of resistance] ? 📏

Hint: not ignore

Answer 5

• in the case of resistance, the zero error needs to be subtracted from all our readings.

Question 6

Why type of errors is there, in the required practical relating to resistance ? 📏

Hint: zero, resistance

Answer 6

• zero error- the crocodile clip isn’t exactly at zero, since it extremely hard to do this.
• there is some resistance caused by the contact between the crocodile clip and the wire- causing zero error

Question 7

What other problems are there in the required practical, relating to resistance ? 🔥

Answer 7

• if the temperature of the wire increases, the resistance will also increase- affecting our results.
• therefore, a low potential difference can be used- this keeps the current low, reducing any heating in the wire.
• and only turn the current on, when taking a reading. [turn off the current between readings]

Question 8

Other than ____ error, there is another error about investing resistance.

Explain how this can be solved. 📏 🔥

Answer 8

• use a low potential difference- which keeps the current low, reducing any heating in the wire.
• and only turn the current on, when taking a reading. [turn off the current between readings]

Question 9

Explain how a variable resistor can be used in the required practical, relating to resistance.

Hint: control

Answer 9

• using the slider, the length of the wire that the current runs through can be changed.
• A variable resistor can be used to control the potential difference across the lamp.
• by increasing the resistance, it can make the light dimmer.

Question 10

Describe [the required practical of] how to determine the densities of regular objects [3] 🧊

Answer 10

• measure the length, width and height of the regular object using a ruler- to calculate the volume
• then measure the mass of the regular object using a balance, to calculate the density of the regular object
• and then use the calculated mass and volume of the regular object, to calculate density of the regular object [by using a calculator, and the density equation.]

Question 11

Describe [the required practical of] how to determine the densities of irregular objects 🏺[6]

Answer 11

• first calculate the mass of the irregular object using a balance, to calculate the density
• then measure the volume of the irregular object, by using a displacement can [eureka can]
• fill a eureka can with water [this has a spout, so water can fill out of the can] and gently [lower and] submerge the object into the water, by using a string
• this will then cause water to be displaced and flow out of the can, through the spout- into the measuring cylinder
• measure the volume of the water displaced [and the volume of the measuring cylinder,] to calculate the volume of the irregular object.
• then calculate the density of the irregular object, by using the calculated mass and volume [and calculate the density, using a calculator and the density equation]

Question 12

Describe the required practical of how to determine the density, of a liquid. 💧[5]

Answer 12

• place a empty measuring cylinder onto a balance, and zero it.
• then measure the mass of the empty measuring cylinder, using a balance.
• pour 10ml of the liquid, into the measuring cylinder and record the combined mass of the liquid and the measuring cylinder. [record volume of
  liquid]
• to calculate the liquid’s mass, subtract the mass of the cylinder from the combined mass [of liquid and cylinder]
• then plug the mass and volume of the liquid into the density equation, and calculate the density of the liquid.