Meter Bridge or Wheatstone Bridge With Pencil Jockey
Product Code : EL-EAE-10289
Quick answer: The meter bridge (slide-wire Wheatstone bridge) is used in physics practicals to find an unknown resistance and the specific resistance of a wire from the balance point on a one-metre wire. It has a 24 SWG constantan wire clamped to brass end strips, heavy copper strips with nine brass terminals, and comes with a pencil jockey. Lab Exports manufactures it in Delhi for schools, colleges and universities.
Specifications
| Component | Specification |
|---|---|
| Bridge wire | 24 SWG constantan, stretched along a wooden metre scale |
| Wire ends | Clamped to brass end strips so that end errors are negligible |
| Bridge strips | Heavy copper strip, four-gap |
| End gaps | Closed by removable copper binding pieces held by the terminals |
| Terminals | Nine, heavy brass, lock type |
| Base | 3/4 inch thick laminated base |
| Supplied with | Pencil jockey and lead for connections |
How the meter bridge experiment is done
The meter bridge works on the Wheatstone bridge principle. A known resistance R is placed in one gap and the unknown resistance X in the other, with a cell across the ends of the wire and a galvanometer between the centre strip and the jockey. At the balance point, where the galvanometer shows no deflection, R/X = l/(100 - l), with l the balancing length in cm from the end next to R, so X = R(100 - l)/l.
- Connect a resistance box as the known resistance in the left gap and the wire or resistor under test in the right gap.
- Join a cell and a plug key across the ends of the bridge wire, and a galvanometer between the central terminal and the pencil jockey.
- Touch the jockey gently on the wire at different points, without sliding it, to find the point of zero deflection.
- Record the balancing length l, then interchange R and X and repeat to reduce the effect of end resistance.
- Calculate X; for a wire of length L and radius r, the specific resistance is rho = X x pi r^2 / L.
Choosing a known resistance that brings the balance point close to the 50 cm mark gives the most sensitive result, because the percentage error in l is smallest there.
Key features
- 24 SWG constantan bridge wire, clamped to brass end strips to keep end errors negligible.
- Heavy copper strips forming a four-gap bridge, with end gaps closed by removable copper binding pieces.
- Nine heavy lock-type brass terminals for low contact resistance at every connection.
- Wooden metre scale under the wire for reading the balancing length directly.
- 3/4 inch thick laminated base that keeps the bridge steady on the bench.
- Pencil jockey and connecting lead supplied with the bridge.
Documentation and supply
Installation instructions and a manual are supplied with the apparatus. Most Lab Exports products carry a one-year manufacturer warranty.
Lab Exports manufactures the meter bridge at its works in Laxmi Nagar, Delhi, and supplies it to schools, colleges and universities in India and 60+ countries, handling the export documents for each shipment. More about the company is on the About Lab Exports page.
Related Electrical and Electronics products
- Rheostat Nichrome Wire Groove Type (EL-EAE-10288)
- Potentiometer with Jockey Pencil (EL-EAE-10290)
- Rheostat Constantine (Eureka) Wire (EL-EAE-10287)
- Pencil Jockey (EL-EAE-10291)
- Resistance Box Electronic Type (EL-EAE-10286)
- Circuit Board Junior (EL-EAE-10292)
The full range is in the Electrical and Electronics section of the Physics Lab range.
Frequently asked questions
What is the formula for unknown resistance on a meter bridge?
At balance, X = R(100 - l)/l, where R is the known resistance, X the unknown resistance and l the balancing length in cm measured from the end next to R.
Which wire is used on this meter bridge?
The bridge wire is 24 SWG constantan, whose resistance changes very little with temperature. It is clamped to brass end strips.
Is the jockey included with the meter bridge?
Yes. A pencil jockey and a lead for connections are supplied with the bridge.
What is the price of the meter bridge?
Prices are not published on the website. Add the meter bridge to the Enquiry Cart with the Add To Cart button on this page, or email [email protected] with the house code EL-EAE-10289 and the quantity, to receive a quotation.
Does Lab Exports manufacture the meter bridge?
Yes. Lab Exports manufactures the meter bridge at its works at 11/315, Lalita Park, Laxmi Nagar, Delhi 110092, under house code EL-EAE-10289.
Request a quote
Email [email protected] with the house code EL-EAE-10289 and the quantity, or add the meter bridge to the Enquiry Cart with the Add To Cart button on this page. Tender buyers can also see the Tenders and OEM page.
