14 Current of Electricity

What is the resistance of Y when its length is doubled and diameter three times larger? 2018PPp1q31

Evan Toh

Nov 41 min read

What is the resistance of Y when its length is doubled and diameter three times larger? 2018PPp1q31

When question states that radius or diameter is increased by 3 times, that note that cross-sectional area does not increase by 3 times....

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2007PPp1q28 2019PPp1q33 - Which V-I readings are for torch lamp?

Evan Toh

Oct 251 min read

2007PPp1q28 2019PPp1q33 - Which V-I readings are for torch lamp?

2019PPP1Q33 Ans: Option B 2007PPP1Q28 Ans: Option B Torch lamp or bulb is a non-ohmic conductor . The V-I graph has an increasing...

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2024 Specimen Paper 6091 P1 Q30 Filament bulb graphs

Evan Toh

Oct 231 min read

2024 Specimen Paper 6091 P1 Q30 Filament bulb graphs

When comes to filament lamp, the non-ohmic characteristic properties comes to mind. But for this quesitons, you have to understand that...

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2010SPP2Q12 Fuel gauge using variable resistor

Evan Toh

Oct 221 min read

2010SPP2Q12 Fuel gauge using variable resistor

Solutions: As the fuel level drops, the float which stays on the fuel surface will descend. The rod which is attached to the float will...

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When a thermistor is connected in series with a fixed resistor, how to explain the p.d. varies as resistance temperature changes?

Evan Toh

Oct 211 min read

When a thermistor is connected in series with a fixed resistor, how to explain the p.d. varies as resistance temperature changes?

When two components are connected in series, where one is a fixed resistor and the resistance of the other can vary (e.g. thermistor,...

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Factors that affect the resistance of a conductor

Evan Toh

Oct 211 min read

Factors that affect the resistance of a conductor

In general, assuming temperature of a conductor is constant, the resistance of a conductor is affected by 1) length (L) – [L increases, R...

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2021PPp1q36 DC circuit, which circuit has a potential difference between P and Q

Evan Toh

Oct 151 min read

2021PPp1q36 DC circuit, which circuit has a potential difference between P and Q

Do you understand why there is a potential difference between P and Q? What if you are to find the potential difference between P and Q?...

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2012PPp2q07 - Find the p.d. across A and C

Evan Toh

Oct 151 min read

2012PPp2q07 - Find the p.d. across A and C

Instead of the usual finding of potential difference across a component, in this question, you are required to find the p.d. across two...

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Wrong connection to the terminals of ammeter or voltmeter

Evan Toh

Aug 310 min read

Wrong connection to the terminals of ammeter or voltmeter

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Different wires for different connection points

Evan Toh

Aug 310 min read

Different wires for different connection points

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Evan Toh

Aug 310 min read

How to read the voltmeter

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Evan Toh

Aug 310 min read

How to read the ammeter

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Evan Toh

Dec 31, 20231 min read

Finding total effective resistance

For resistors connected in series, the total resistance is the sum of all resistance. Re = R1 + R2 + R3 For resistors in parallel, the...

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Evan Toh

Dec 31, 20230 min read

Common Electrical Symbols

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Evan Toh

Dec 31, 20230 min read

Ohmic and Non-ohmic conductors

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What is the current in wire OP? Is it flowing from O to P or P to O?

Evan Toh

Nov 30, 20231 min read

What is the current in wire OP? Is it flowing from O to P or P to O?

Solutions: Option B Whatever that goes in has to come out. With this basic concept, you will be able to solve this question easily....

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Modification to ammeter to measure bigger current

Evan Toh

Nov 30, 20231 min read

Modification to ammeter to measure bigger current

Sensitivity of the ammeter means that how small a current the ammeter can measure. Example, if the original set up is 0.2 A per division,...

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Evan Toh

Nov 30, 20231 min read

2007PPP1Q27 brightness of bulb

Solutions: Option B As lamp X is thicker and shorter , these two factors make the resistance of X lower than Y . Recall: Length...

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Electromotive force (e.m.f.) vs potential difference (p.d)

Evan Toh

Nov 30, 20230 min read

Electromotive force (e.m.f.) vs potential difference (p.d)

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Evan Toh

Nov 30, 20231 min read

Finding effective resistance when a wire is bent into different shapes

The concepts needed to solve such questions Length increases, resistance increases and vice versa. Finding resistors in parallel and in...

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