A resistor is connected to a power supply - Edexcel - GCSE Physics Combined Science - Question 5 - 2018 - Paper 1

To calculate the time, we can use the formula for electric current:

$I = \frac{Q}{t}$

Where:

• $I$ is the current in amperes (200 mA = 0.2 A)
• $Q$ is the charge in coulombs (42 C)
• $t$ is the time in seconds.

Rearranging the formula gives:

$t = \frac{Q}{I} = \frac{42\, C}{0.2\, A} = 210\, s$

To convert seconds into minutes:

$t = \frac{210}{60} = 3.5\, minutes$

Total energy (E) can be calculated using the formula:

$E = V \times Q$

Where:

• $V$ is the potential difference (6.0 V)
• $Q$ is the total charge (42 C)

Substituting the values gives:

$E = 6.0 V \times 42 C = 252 J$

The resistor becomes warm due to the collisions between the flowing electrons and the lattice structure of the resistor material. As electrons move through the resistor, they collide with atoms in the lattice, converting some of their kinetic energy into thermal energy. This increase in thermal energy raises the temperature of the resistor.

Using Ohm’s law:

$R = \frac{V}{I}$

Given:

• Potential difference $V = 6.0 V$
• Current $I = 1.2 A$

Substituting gives:

$R = \frac{6.0 V}{1.2 A} = 5 \Omega$

Since each resistor is $100 \Omega$, the only configuration that maintains a total resistance of $5 \Omega$ with a 6.0V supply while allowing $1.2 A$ of current is if the resistors are arranged in parallel, where:

$\frac{1}{R_{total}} = \frac{1}{R_1} + \frac{1}{R_2}$

Thus, the resistors must be connected in parallel.