Current, potential difference, power and resistance test questions

1

An LED is rated at \(2.3V\) and draws a current of \(32mA\), but it needs to be operated from a \(12V\) supply.

A circuit containing a 12 volt cell, a resistor and a light emitting diode (LED).

What is the voltage (potential difference) across the series resistor R?

2

An LED is rated at \(2.3V\) and draws a current of \(32mA\), but it needs to be operated from a \(12V\) supply.

A circuit containing a 12 volt cell, a resistor and a light emitting diode (LED).

Calculate the value of resistance \(R\) which must be connected in series to ensure the LED operates at its rating.

3

An LED is rated at \(2.3V\) and draws a current of \(32mA\), but it needs to be operated from a \(12V\) supply.

A circuit containing a 12 volt cell, a resistor and a light emitting diode (LED).

Calculate the power rating of the LED when operating normally.

4

A voltage divider is set up to monitor temperature as shown.

A circuit containing a 7 volt cell, a 27 kilo ohm thermistor and a 52 kilo ohm resistor with a voltmeter across it.

Calculate the potential difference across the \(52k\Omega\) resistor.

5

The temperature rises and the resistance of the thermistor decreases to \(1.9k\Omega\).

A circuit containing a 7 volt cell, a 1.9 kilo ohm thermistor and a 52 kilo ohm resistor with a voltmeter across it.

Calculate the output voltage measured by the voltmeter at this new temperature.

6

What is the total resistance of the network below?

Network of 3 resistors with R1 = 32 Ohms, and R2 = 12 Ohms, R3 = 24 Ohms (R2 and R3 in parallel to each other, and R1 and R2 are in series with each other)

7

The network below is connected to a \(15V\) supply. Calculate the current in the \(24\Omega\) resistor?

Network of three resistors: R1 = 12 Ohms, R2 = 36 Ohms, R3 = 24 Ohms, with R1 & R2 in series with each other, R3 in parallel to these

8

What is the total resistance of the network below?

Network of 4 resistors R1 = 12 Ohms, R2 = 36 Ohms, R3 = 6 Ohms, R4 = 18 Ohms. R1 & R2 in series, R3 parallel to R1, R4 parallel to R2

9

A potential divider is set up with resistances as shown.

A circuit diagram with a 24 Volt power source, a 270 kilo ohm resistor and 670 kilo ohm resistor in series.

Calculate the potential across the \(670k \Omega\) resistor.

10

A voltmeter of resistance \(960k \Omega\) is connected across the \(670k \Omega\) resistor.

Calculate the measured potential difference across the \(670k \Omega\) resistor taking account of the resistance of the voltmeter.

A circuit diagram with a 24 Volt power source, a 270 kilo ohm resistor and 670 kilo ohm resistor in series. There is a 960 kilo ohm Voltmeter across the 670 kilo ohm resistor.