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 GCSE     Measure     >Current<     Frequency Meter     Logic Probe     Multimeter     Oscilloscope     Power     Voltmeter

# Measure Current

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GCSE    Measurements    Questions 0 to 5   -->  View All

Connect an ammeter in series. The voltage across an ideal ammeter is zero.

## Ammeter Facts

• Connect the ammeter in series with the circuit being measured.
• Ammeters measure the current THROUGH a component. Connect the ammeter in series with the device being measured.
• Voltmeters measure the potential difference (voltage) ACROSS a component. Connect the voltmeter in parallel with the device being measured.

## An Ideal Ammeter

• has zero volts across it
• has a resistance of zero Ohms
• does not affect the circuit it is measuring.
• real ammeters have resistances close to zero.
• Therefore very large currents can flow through the ammeter if it is wired up wrongly.
• Most ammeters are protected by a fuse.

## Measuring Current

### CORRECT

Flash Animation: How the experts do it!

### WRONG

Flash Animation: How the twonks do it!

Twonk is also the noise made by the pointer in an analogue ammeter smashing itself against the end stop shortly before the meter burns out.

The ammeter must be placed in SERIES with the component who's current needs to be measured.

Break the circuit by removing a wire and replace the wire with the ammeter. In this way, the current flows through the ammeter and can be measured.

## Making Safe use of Multimeters

Many beginners play multimeter roulette.

If they are lucky, they only blow the fuse inside the meter. It is also possible to destroy the meter. To play this game,

• connect the meter before setting it to the correct range.
• with the circuit switched on, randomly turn the range knob until the meter is destroyed or the fuse blows
• Clueless!

You are most likely to destroy the meter when trying to measure current. Remember that the current you are measuring must flow through the meter.

• Set the meter to the correct range before connecting it up.
• Set the meter to the correct range before switching on the circuit.
• If measuring voltage, set the meter to the highest voltage you are likely to encounter. Later you can switch to lower voltage settings if necessary.
• If you are measuring current, set the meter to the highest current you are likely to encounter.
• Later you can switch to lower current settings if necessary.
• Resistance can only be measured if the resistor is not wired up in a circuit.

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 CloseEscapeX Q: qNum of last_q     Q ID: Question ID         Score: num correct/num attempts         Date Done

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