## NTU Electrodynamics

- Category: pre Universities
- Written by fisikastudycenter

Questions and solution for nanyang technological University Singapore Entrance Examination preparation in physics on the syllabus of Electricity and magnetism - Current of electricity.

**Question 1**

Given an electric circuit below

What is the magnitude of current in the 40 Ω resistor?

A. 0.41 A

B. 0.33 A

C. 0,77 A

D. 1.30 A

**Solution**

We may use the shortcut to solve this question.

The first find the total resistance for the circuit:

Then the potential difference between a and b points:

Applying kirchoff law to find I

**Question 2**

Given an electric circuit shown below fugure.

In the circuit, the power dissipated in the 6 Ω resistor as heat is 6 watt. What is the value of resistance X in above circuit?

**Solution**

The power P which is dissipated in 6 Ω is 6 watt.

P = I^{2}R

6 = I^{2} (6)

I = 1 Ampere

The voltage across 6 Ω or V_{AB} = IR = (1A)(6 Ω) 6 volt. So then the voltage across BC, V_{BC} = 12 volt − 6 volt = 6 volt.

X and 8 Ω in parallel connection so then the voltage across is the two resitors are same value and the currents pass:

I_{2} = V/R = 6 / 8 = 3 / 4 = 0.75 A

I_{1} = I − I_{2} = 1 − 0,75 = 0.25 A

The resistor X = V/I = 6 / 0.25 = 24.0 Ω